gpu: ion: Also shrink memory cached in the deferred free list

When the system is low on memory, we want to shrink any cached
system memory ion is holding.  Previously we were shrinking memory
in the page pools, but not in the deferred free list.  This patch
makes it possible to shrink both.  It also moves the shrinker
code into the heaps so they can correctly manage any caches they
might contain.

Change-Id: I177f587f999a5220eddbf7af94745aae736cac75
Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>
Git-commit: 072beca55150c0c0b652bbb24267da271e0bdf19
Git-repo: https://android.googlesource.com/kernel/common
[mitchelh@codeaurora.org: minor context fixups due to MSM changes]
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
gpu: ion: Add buffer flag to skip page pooling on free

Currently, when we free a buffer it might actually just go back into a
heap-specific page pool rather than going back to the system. This poses
a problem because sometimes (like when we're running a shrinker in low
memory conditions) we need to force the memory associated with the
buffer to truly be relinquished to the system rather than just going
back into a page pool.

There isn't an obvious use case for this flag by Ion clients. The main
use case right now is to provide a mechanism for the deferred free code
to force stale buffers to bypass page pooling.

Change-Id: I724f89cc037083fe8576784363caa18a34e8705a
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
gpu: ion: create separate heap and client debugfs directories

It can be slightly annoying to figure out which files under the ion
debugfs directory are heap debug files and which ones are client debug
files. Create separate subdirectories under ion to hold the different
types of debug files.

Change-Id: Ic773ab619ef94b9b4d0f3794def9d37645c7c212
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>