msm: kgsl: Support offset and size for cache operations

Currently, IOCTL_KGSL_GPUMEM_SYNC_CACHE performs cache
operations on the entire memdesc. This change adds
support for performing the cache operation on a range
of memory defined by an offset and size

Change-Id: Icd8bf6f5a5c1a0335c6d278b950e19bdda0c95f6
Signed-off-by: Sushmita Susheelendra <ssusheel@codeaurora.org>