msm: kgsl: Add 'strict memory' debug mode

Add a root only debug mode to force GFP_NORETRY for all page_alloc
memory allocations. This lets stress applications allocate lots of
memory and test error paths without worrying about getting on the
wrong side of the OOM killer.

Enable it like so:  "echo 1 > /d/kgsl/strict_memory"

Change-Id: Ic0dedbadbb627342640c90c589fa384eaaafe245
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>