drm/amd/display: Fix DMUB reset sequence for DCN401

drm/amd/display: Fix DMUB reset sequence for DCN401

[WHY]
It should no longer use DMCUB_SOFT_RESET as it can result
in the memory request path becoming desynchronized.

[HOW]
To ensure robustness in the reset sequence:
1) Extend timeout on the "halt" command sent via gpint, and check for
controller to enter "wait" as a stronger guarantee that there are no
requests to memory still in flight.
2) Remove usage of DMCUB_SOFT_RESET
3) Rely on PSP to reset the controller safely

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Dillon Varone <Dillon.Varone@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>