msm: kgsl: Support user-specified caching hints

The user allocating memory can provide hints for the caching
settings when said buffer is mapped on the user side. Try
to obey the cache settings when applicable.  The user will
be responsible for handling cache management both to and
from the GPU so add a new ioctl IOCTL_KGSL_GPUMEM_CACHE_SYNC to
support both directions (the old IOCTL_KGSL_SHAREDMEM_FLUSH_CACHE)
only handled flushing, not invalidating. The legacy ioctl still
works it just does what it says it does - a cache flush.

Change-Id: Ic0dedbad55ce82f2b01ebc56de30d4649e2e7311
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>