drm/msm/adreno: a5xx: Explicitly program the CP0 performance counter

Even though the default countable for CP0 is CP_ALWAYS_COUNT (0),
program the selector during HW initialization in an effort to be
up front about which counters are programmed and why.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>