dt-bindings: display: mediatek: merge: add additional prop for mt8195

add MERGE additional properties description for mt8195:
1. async clock
2. fifo setting enable
3. reset controller

Signed-off-by: jason-jh.lin <jason-jh.lin@mediatek.com>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>