[WHY]
PSP can access DCN registers during command submission and we need
to ensure that DCN is not in PG before doing so.

[HOW]
Add a callback to DM to lock and notify DC for idle optimization exit.
It can't be DC directly because of a potential race condition with the
link protection thread and the rest of DM operation.

Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Acked-by: Alex Hung <alex.hung@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>