drm/msm/adreno: push dump/show stuff to base class

Add ptr to list of interesting registers to 'struct adreno_gpu' and use
that to move most of the debugfs show and register dump bits down into
adreno_gpu.  This will avoid duplication as support for additional
adreno generations is added.

Signed-off-by: Rob Clark <robdclark@gmail.com>