drm/amd/display: 4k split black out due to incorrect cursor

- add handling to program both cursor for left and right pipe
- add guard to disable cursor in case where cursor isn't visible to prevent pipe hang

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