[Why]
Dmub will cache the video position data during PSR-SU enable.
The dmub will use an outdated MPO video position if user try
to drag the video window and it will cause video glitch.

[How]
Disable the PSR-SU temporarily while user drag the video window.
The PSR-SU will be re-enabled after the video window is stable.
Reviewed-by: Sun peng Li <Sunpeng.Li@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Tom Chung <chiahsuan.chung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>