msm: kgsl: Enable GPU system cache usage on A640

System cache feature on A640 is different than A630.
We still use the LLCC driver API to activate/deactivate
GPU slices. But, the SCID configuration registers
have moved from CX_MISC to GBIF register space. Also,
the GPU HTW SCID cannot be configured via these registers
on A640 because of the way MMU500 is integrated. The
GPU HTW SCID will be configured via NoC override in
the xbl image. Lastly, the page attributes are no longer
configured via register write. They are now specified
in the smmu pagetable entries.

Change-Id: Ic47fcc96a704cf50b84f14177225a75eab2a82aa
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>