msm: kgsl: Add support for GPU System Cache usage

Activate and deactivate the GPU slice in the system
cache upon GPU power collapse/restore. Configure the
SCIDs for the slices used by the GPU. Currently, the
GPU uses one slice for all its blocks.
Also enable the right memory attributes for a buffer
to be allocated into the system cache. The memory
attributes used are outer-cacheable, read-allocate,
write-no-allocate.

CRs-Fixed: 1081617
Change-Id: I54d5ddce8056c0ef491a21bb19ce9fd9e30a0540
Signed-off-by: Sushmita Susheelendra <ssusheel@codeaurora.org>