drm/amd/display: Add dc_dmub_srv helpers for in/out DMCUB commands

[Why]
We added these in DMCUB for runtime feature detection
but we didn't have helpers to call these with DC error
handling/logging.

[How]
Add helpers.

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Eric Yang <eric.yang2@amd.com>
Acked-by: Qingqing Zhuo <Qingqing.Zhuo@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>