msm: kgsl: Cleanup the adreno SOC HW probe

The code to probe the sometimes used HW revision only needs to live in
adreno.c and we don't need to store a persistent member in adreno_device.
Localize all the code and pass the HW revision into the functions that
need it.

Change-Id: Ic0dedbaddafe258f6b6510f68867cff636963315
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>