Add MTK mutex support for MT8186 SoC.
We need MTK mutex to control timing of display modules and there
are two display pipelines for MT8186 including internal and external
display.

MTK mutex for internal display:
- Timing source: DSI
- Control modules: OVL0/RDMA0/COLOR0/CCORR/AAL0/GAMMA/POSTMASK0/DITHER

MTK mutex for external display:
- Timing source : DPI
- Control modules: OVL_2L0/RDMA1
Signed-off-by: Yongqiang Niu <yongqiang.niu@mediatek.com>
Signed-off-by: Rex-BC Chen <rex-bc.chen@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>