Revert "drm/amd/pm: resolve reboot exception for si oland"

This reverts commit e490d60a.

This causes hangs on SI when DC is enabled and errors on driver
reboot and power off cycles.

Closes: drm/amd#3216
Closes: drm/amd#2755


Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org