msm: kgsl: Move a3xx perfcounters to target specific

Add support for per-group enable and read functions and move all of the
3xx perfcounters to target specific code with specialized functions.
The a3xx functions are the most "non-standard" of the bunch because of
the freeze/unfreeze wrappers we need for most registers.

Change-Id: Ic0dedbad110eeaf667f6f44d809d4cd90942451a
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>