msm: kgsl: Move always on timer reads to target specific code

Instead of using adreno_readreg and a bunch of if statemnts, move the
always on timer functionality to the target specific code where it
belongs. This lets us do local variations without a bunch of hacks.

Change-Id: Ic0dedbad91b6a46f55c813f83360cb205bf5e357
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>