msm: kgsl: Define register offset array

Different adreno cores have different offsets for same register.
These registers are referenced in code areas which are common to
all adreno cores. Hence, they should be referenced with a variable
instead of using a constant to make things more generic. This makes
the code more suitable for accomodating future cores.

Change-Id: Ie3d387d7cf767d46eea90e0fecdbba88dad97860
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>