drm/amd/display: Block timing sync for different signals in PMO

PMO assumes that like timings can be synchronized, but DC only allows
this if the signal types match.

Reviewed-by: Austin Zheng <austin.zheng@amd.com>
Signed-off-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 29d3d6af)
Cc: stable@vger.kernel.org