arm64: dts: rockchip: remove unused pin settings from px30

These are unused gpio-settings for specific function pins, that
are not used by anything and only clutter up the dtsi.
They can be re-added when a relevant user is added.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20190917082659.25549-8-heiko@sntech.de