drm/amd/display: Fixing some fallout from dc_target removal

Also avoid allocating memory dce110_set_output_transfer_func
if not needed

Signed-off-by: Leon Elazar <leon.elazar@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>