drm/amd/display: Wait before sending idle allow and after idle disallow

[Why]
We want acknowledgment of the driver idle disallow from DMCUB before
continuing with any further programming.

For idle allow we want to minimize the chance of DMCUB actively
interacing with other firmware components on the system (eg. PMFW)
at the same time.

[How]
Ensure that DMCUB isn't in the middle of processing other command
submissions prior to allowing idle and after disallowing idle by
inserting a wait before the allow and by changing the wait type for
the idle disallow.

Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>