drm/amd/display: Check cursor address before program.

Program cursor attributes during set mode is only needed
in case of pipe slipt, bottom pipe should be programmed
same as top pipe. Need to program if address is 0.

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>