drm/amd/display: Set PSR level to enable ALPM by default

drm/amd/display: Set PSR level to enable ALPM by default

[Why & How]
While support ALPM, do ALPM state transition while PSR entry/exit.
ALPM is needed for PSR-SU feature, and since the function is ready,
we'd enable it by default.

- Add psr level definition to enable/disable ALPM and set ALPM
  powerdone mode.
- Enable ALPM by default

Signed-off-by: David Zhang <dingchen.zhang@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>