drm/amd/display: only fill dirty rectangles when PSR is enabled

Currently, we are calling fill_dc_dirty_rects() even if PSR isn't
supported by the relevant link in amdgpu_dm_commit_planes(), this is
undesirable especially because when drm.debug is enabled we are printing
messages in fill_dc_dirty_rects() that are only useful for debugging PSR
(and confusing otherwise). So, we can instead limit the filling of dirty
rectangles to only when PSR is enabled.

Reviewed-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>