dt-bindings: clock: sun50i-a64-ccu: Add PLL_VIDEO0 macro

Allwinner A64 HDMI PHY clock has PLL_VIDEO0 as a parent.

Include the macro on dt-bindings so-that the same can be used
while defining CCU clock phandles.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>