dt-bindings: rockchip,vop2: Add more endpoint definition

There are 2 HDMI, 2 DP, 2 eDP on rk3588, so add
corresponding endpoint definition for it.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20231211115907.1785377-1-andyshrk@163.com