[Why]
DC can utilize the DMUB server to send commands to the DMUB but it's
the DM responsibility to pass it the service to use.

[How]
Create the dc_dmub_srv after we finish initializing the dmub_srv.
Cleanup the dc_dmub_srv before destroying the dmub_srv or dc.
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Hersen Wu <hersenxs.wu@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>