clk: mediatek: Add MT8186 vencsys clock support

Add MT8186 vencsys clock controller which provide clock gate
control for video encoder.

Signed-off-by: Chun-Jie Chen <chun-jie.chen@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Miles Chen <miles.chen@mediatek.com>
Link: https://lore.kernel.org/r/20220409132251.31725-13-chun-jie.chen@mediatek.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>