drm/amd/display: Fix DPIA outbox timeout after S3/S4/reset

commit af6902ec upstream.

[Why]
The HW interrupt gets disabled after S3/S4/reset so we don't receive
notifications for HPD or AUX from DMUB - leading to timeout and
black screen with (or without) DPIA links connected.

[How]
Re-enable the interrupt after S3/S4/reset like we do for the other
DC interrupts.

Guard both instances of the outbox interrupt enable or we'll hang
during restore on ASIC that don't support it.

Fixes: 6eff272d

 ("drm/amd/display: Fix DPIA outbox timeout after GPU reset")

Reviewed-by: Jude Shih <Jude.Shih@amd.com>
Acked-by: Pavle Kotarac <Pavle.Kotarac@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>