clk: mediatek: add VDOSYS1 clock

Add the clock gate definition for the DPI1 hardware
in VDOSYS1.

The parent clock "hdmi_txpll" is already defined in
`mt8195.dtsi`.

Signed-off-by: Pablo Sun <pablo.sun@mediatek.com>
Signed-off-by: Guillaume Ranquet <granquet@baylibre.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20220919-v1-2-4844816c9808@baylibre.com


Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>