drm/amd/display: Rework registers tracepoint

amdgpu_dc_rreg and amdgpu_dc_wreg are very similar, for this reason,
this commits abstract these two events by using DECLARE_EVENT_CLASS and
create an instance of it for each one of these events.

Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>