drm/udl: properly check for error pointers

The drm_prime_pages_to_sg() function never returns NULL pointers, only
error pointers and valid pointers.

BUG=chromium:402599
TEST=emerge-link_freon chromeos-kernel-3_8
Signed-off-by: Haixia Shi <hshi@chromium.org>

Change-Id: Ie80529b008f46e09bc1e0828862e3613a3c95a3c
Reviewed-on: https://chromium-review.googlesource.com/231704
Tested-by: Haixia Shi <hshi@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Commit-Queue: Haixia Shi <hshi@chromium.org>
Merge branch 'chromeos-3.8' of https://chromium.googlesource.com/chromiumos/third_party/kernel into chromeos-3.8
CHROMIUMOS: mac80211: Allow IE injection

Allow userspace to append an un-validated footer to the IEs
sent in outgoing beacons in AP mode.  Used to duplciate AP
behavior in testing scenarios.

Signed-off-by: Paul Stewart <pstew@chromium.org>

BUG=chrome-os-partner:33662
TEST=Upcoming autotests + Manual: Start hostapd and use
over-the-air capture to display beacons while changing the
content of /sys/kernel/debug/ieee80211/phy0/beacon_footer

Change-Id: I992c1c8466edcb191358724ea9c2067f85863985
Reviewed-on: https://chromium-review.googlesource.com/232362
Reviewed-by: Peter Qiu <zqiu@chromium.org>
Commit-Queue: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
Merge branch 'chromeos-3.8' of https://chromium.googlesource.com/chromiumos/third_party/kernel into chromeos-3.8