drm/amd/display: Allow idle opts for no flip case on PSR panel

drm/amd/display: Allow idle opts for no flip case on PSR panel

[Why & How]
There is a corner case where a single PSR panel
fails to enter idle optimizations if the panel
is not flipping (no planes or DPMS_OFF == true).
This is because the panel will not enter PSR if it's
not flipping, but this will prevent the FW idle opt
path from being executed. To handle this case we will
allow entry to idle opt from driver side even when a
PSR panel is connected under the following scenarios:
	1. Only a single PSR panel is connected
	2. PSR panel is not flipping

Reviewed-by: Samson Tam <samson.tam@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>