msm: kgsl: Make an interface to write A5XX clock gating registers

We will have more 5XX targets with ever increasing hardware clock
gating requirements. Rather than piling on if/else statements create
a generic infrastructure to write the correct sets of registers.

Change-Id: Ic0dedbad0a18df87a68858045b2662b3470b1276
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>