[Why]
To process SET_CONFIG transactions with DMUB using inbox1 and
outbox1 mail boxes.

[How]
1) Added inbox1 DPIA command subtype DMUB_CMD__DPIA_SET_CONFIG_ACCESS to
   issue SET_CONFIG command to DMUB in dc_process_dmub_set_config_async().
   DMUB processes the command with DPIA sends reply back immediately or
   in an outbox1 message triggering an outbox1 interrupt to driver.
2) DMUB posts SET_CONFIG reply as an Outbox1 message of type
   DMUB_OUT_CMD__SET_CONFIG_REPLY.
3) The dmub async to sync mechanism for AUX is modified to accommodate
   SET_CONFIG commands for both command issue and reply code paths.
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Wayne Lin <Wayne.Lin@amd.com>
Acked-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Meenakshikumar Somasundaram <meenakshikumar.somasundaram@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>