drm/amd/display: add DMUB registers to crash dump diagnostic data.

[WHY]
Ability to triage DMCUB is improved with availability of certain
dmub registers not currently captured in crash dump diagnostic data.

[HOW]
Add dmub registers to diagnostic data collection.

Thanks Nicholas Kazlauskas for awesome input on this!

Signed-off-by: Ashley Thomas <Ashley.Thomas2@amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>