Add cmdq support for mtk-mmsys config API.
The mmsys config register settings need to take effect with the other
HW settings(like OVL_ADAPTOR...) at the same vblanking time.
If we use CPU to write the mmsys reg, we can't guarantee all the
settings can be written in the same vblanking time.
Cmdq is used for this purpose. We prepare all the related HW settings
in one cmdq packet. The first command in the packet is "wait stream done",
and then following with all the HW settings. After the cmdq packet is
flush to GCE HW. The GCE waits for the "stream done event" to coming
and then starts flushing all the HW settings. This can guarantee all
the settings flush in the same vblanking.
Signed-off-by: Nancy.Lin <nancy.lin@xxxxxxxxxxxx>