arm64: dts: rockchip: Rename hdmi-con to hdmi0-con for Cool Pi CM5 EVB

There are two hdmi connector on Cool Pi CM5 EVB, the current supported
is hdmi0, assign corresponding index to it. It will be convenient for
us to add support for another one.

Signed-off-by: Andy Yan <andyshrk@163.com>
Link: https://lore.kernel.org/r/20250419121326.388298-1-andyshrk@163.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>