[Why]
PSR (Panel Self-Refresh) is a power-saving feature for eDP panels.
The feature has support in DMCU (Display MicroController Unit).
DMCU/driver communication is implemented in DC.
DM can use existing DC PSR interface to use PSR feature.

[How]
- Read psr caps via dpcd
- Send vsc infoframe if panel supports psr
- Disable psr before h/w programming (FULL_UPDATE)
- Enable psr after h/w programming
- Disable psr for fb console
Signed-off-by: Roman Li <Roman.Li@amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>