msm: kgsl: Add initial A6XX device support

Create the basic framework for the A6xx hardware layer in KGSL.
Add basic A6xx initialization sequence, which includes loading
the firmware, a number of register writes and CP init. Also,
add the interrupts and handlers for A6x.

Change-Id: Ic723506e9659b82c708a739ceb12d78cbeec2feb
Signed-off-by: Shrenuj Bansal <shrenujb@codeaurora.org>