drm/mediatek: support CMDQ interface in ddp component

The CMDQ (Command Queue) in some Mediatek SoC is used
to help update all relevant display controller registers
with critical time limation.
This patch add cmdq interface in ddp_comp interface,
let all ddp_comp interface can support cpu/cmdq function
at the same time.

Signed-off-by: YT Shen <yt.shen@mediatek.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Bibby Hsieh <bibby.hsieh@mediatek.com>
Signed-off-by: Yongqiang Niu <yongqiang.niu@mediatek.com>
Signed-off-by: CK Hu <ck.hu@mediatek.com>