drm/amd/display: Fixed switching mode half screen gamma incorrect.

	Half screen gamma setting and cursor are incorrect
	when switching mode through win+p due to wrong programming
	gamma sequence (In case of bottom pipe, gamma and cursor are
	programmed before front end programmed, pipe is power gated).

	change:
	1. Cache curor attributes to stream
	2. Move set gamma and cursor inside front end
	   programming.

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>