drm/amd/display: WA for 3 display play video hot plug.

	Three monitor connected and playing a video will
	occupy all 4 pipes, if hot plug forth display,
	commit streams will be failed due to no free pipe
	can be found.
	Work around:
	When forth monitor connected, mark video plane as
	a fake plane, remove it in dc, keep it in dm and
	report address to OS, until OS turn off MPO.

Signed-off-by: Yongqiang Sun <yongqiang.sun@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>