[Why]
When the PSR enabled. If you try to adjust the timing parameters,
it may cause system hang. Because the timing mismatch with the
DMCUB settings.

[How]
Disable the PSR before adjusting timing parameters.

Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Acked-by: Stylon Wang <stylon.wang@amd.com>
Signed-off-by: Tom Chung <chiahsuan.chung@amd.com>
Reviewed-by: Wayne Lin <Wayne.Lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>