drm: msm: a6xx: Dump GBIF registers, debugbus in gpu state

Add the relevant GBIF registers and the debug bus to the a6xx gpu
state. This comes in pretty handy when debugging GPU bus related
issues.

Signed-off-by: Sharat Masetty <smasetty@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>