drm/amd/display: Enable reallow for idle on DCN35

drm/amd/display: Enable reallow for idle on DCN35

[Why]
It was previously disabled for stability purposes, but command
submission causes residency issues in IPS video playback.

[How]
Enable the disallow/reallow pattern back. There's additional checks
now in DMCUB that should make this safer stability wise.

Reviewed-by: Duncan Ma <duncan.ma@amd.com>
Acked-by: Wayne Lin <wayne.lin@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>