drm/msm: Add an ftrace for gpu register access

drm/msm: Add an ftrace for gpu register access

With IFPC, there is a probability of accessing a GX domain register when
it is collapsed, which leads to gmu fence errors. To debug this, we need
to trace every gpu register accesses and identify the one just before a
gmu fence error. So, add an ftrace to track all gpu register accesses.

Signed-off-by: Akhil P Oommen <akhilpo@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/673366/
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>