drm/amd/display: Revert "Increase halt timeout for DMCUB to 1s"

drm/amd/display: Revert "Increase halt timeout for DMCUB to 1s"

This reverts commit 50f040c53ea9 ("drm/amd/display: Increase halt
timeout for DMCUB to 1s")

There's two issues here:
1. Each poll is closer to 10us than 1us so it stalls for 15s on PNP.
2. We're reading the wrong scratch register to check for the HALT code.

Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@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>