gpu: ion: Use list_for_each_safe on error path

On an error, the list of pages is walked and destroyed. Since the list
is being destroyed, use list_for_each_safe to avoid list corruption.

Change-Id: Ia397a11d2d890b3458745820c79df2adaa088ade
CRs-Fixed: 565183
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
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>