ARM: dts: Remove thermistors on all revs of snow

It appears that thermistors were not stuffed on at least some (perhaps
all?) snow-rev4 machines.  It turns out that thermistors were not
particularly useful for thermal throttling on snow since the CPU
temperature is very highly correlated with the thermistor temperature
due to excellent heat spreading on snow.  Rather than forking the snow
dts yet another time between rev3 and rev4, just remove thermistors
from all revs of snow.

BUG=chromium:343569
TEST=On rev3, rev4, and rev5, /var/log/messages after boot shows:
  "Max CPU Freq set to 1700000 (Celsius: 41 )"

Change-Id: Ibff580c3ba55f41d82f231e95eb3c3eb23542ba9
Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/186357
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Reviewed-by: Olof Johansson <olofj@chromium.org>
Reviewed-by: Ilja Friedel <ihf@chromium.org>
Reviewed-by: Jaehoon Kim <jh228.kim@samsung.com>
(cherry picked from commit 2413925bc296ba496ef62a0e8f1ab697f1f68111)
Reviewed-on: https://chromium-review.googlesource.com/186487
drm/exynos: fimd/mixer: synchronously wait for window disable

When a client releases its drm connection, the drm core releases any of
its still-open framebuffers during drm_release() by calling
drm_fb_release(). drm_fb_release() calls drm_framebuffer_remove() for each
fb, which first clears each crtc's fb, and then calls disables all planes,
by calling exynos_disable_plane() [0].  Lastly, it calls
drm_framebuffer_unreference() which calls drm_framebuffer_free() for any
fb that is now no longer referenced. drm_framebuffer_free() calls
exynos_drm_fb_release(), which schedules exynos_drm_fb_release_work_fn()
on a worker thread.

[0]
exynos_disable_plane() ->
 exynos_plane_dpms(DRM_MODE_DPMS_OFF) ->
  exynos_drm_crtc_plane_disable() ->
   manager->win_disable(manager->ctx, zpos) ->
    fimd/mixer_win_disable()

For exynos display controllers (FIMD & MIXER), disabling a plane is always
done asynchronously by clearing a shadowed enable bit.  The display
controller continues to scan out the plane's framebuffer until the next
vblank.

So, some fbs that were just 'disabled' may still be scanning out when
exynos_drm_fb_release_work_fn() gets scheduled and unmaps the fb's gem
objects, leading to iommu faults.

In particular, the xf86-video-armsoc X driver uses a plane for the cursor
sprite.  If X exits without first manually disabling the cursor plane
(e.g., SIGSEGV), this will lead directly to (1) an exynos-fb iommu FAULT
if the cursor was on the internal display, or (2) a mixer iommu FAULT if
the cursor was on an external (HDMI) display.

This is actually a combination of 3 commits, including:
 1) Revert "drm/exynos: fimd: remove the "wait for vblank" infrastructure too"
    23890b5153bcaba47e220329697f85eeaa8cd6b7
 2) Revert "drm/exynos: Remove wait for vblank hacks":
    75d2c2f82ca60883f101e8b919922bc4396328e9
 3) Cherry-pick from 3.4 kernel:
    https://chromium-review.googlesource.com/#/c/170614/

Note: This patch has the downside of always making CRTC window disables
synchronous.  In theory, we could still let window disable be asynchronous
if we had the planes keep a refcount on their FBs.  However, we would
also need to be able to release the refcount when in the irq following the
disable request;  unfortunately there is no infrastructure in place
presently to track (a) "disable" flips (ie flips to no FB) in the
flip_fifo, nor (b) is the flip_fifo able to updates to the cursor plane.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>

BUG=chrome-os-partner:22959, chromium:226244
TEST=export DISPLAY=:0; i=0; \
  while true; do i=$((i+1)); \
   echo "eDP  $i"; xdotool mousemove 100 100; sleep 0.5; pkill -9 X; sleep 10; \
   echo "HDMI $i"; xdotool mousemove 100 900; sleep 0.5; pkill -9 X; sleep 10; \
 done
  => No iommu FAULTS (kcrashes) while executing above X kill loop.
TEST=suspend_stress_test for 20 iterations w/ and w/out HDMI monitor

Change-Id: Ibb45523543b4e451c791428a6d0dfe2abc8d071a
Previous-Reviewed-on: https://chromium-review.googlesource.com/170614
(cherry picked from commit 7a9fe821d8492bb0198ba589b3634a19668cca22)
Reviewed-on: https://chromium-review.googlesource.com/186780
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Tested-by: Daniel Kurtz <djkurtz@chromium.org>
Revert "drm/exynos: fimd/mixer: synchronously wait for window disable"

This reverts commit 0506add9ecaeb7973e391459beb611fbdd155498.

Change-Id: Iac30ad01cfbbe6313053dc7c585deb00129d165e
Reviewed-on: https://chromium-review.googlesource.com/186931
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Tested-by: Daniel Kurtz <djkurtz@chromium.org>