gpu: ion: Fix several issues with page pool

Split out low and high mem pages so they are correctly reported
when the shrinker is called.
Fix potential deadlock caused by holding the page pool lock while
allocationg and also needing that lock from the shrink function

Change-Id: Iaeb45e5d644f1a1a39b491a2941ee9403fff81f0
Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>
Git-commit: 27182f504ce9fa7b10cb2520e8684f7c17bc8c86
Git-repo: https://android.googlesource.com/kernel/common


[lauraa@codeaurora.org: Context differences due to debugfs.
Dropped the debugfs support until we can properly sync back
up]
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>