arm64: dts: rockchip: remove rockchip,grf from vop nodes for px30

arm64: dts: rockchip: remove rockchip,grf from vop nodes for px30

An experimental test with the command below without
additional properties in 'rockchip-vop.yaml' gives this error:

arch/arm64/boot/dts/rockchip/px30-evb.dt.yaml: vop@ff470000:
'power-domains', 'rockchip,grf'
do not match any of the regexes: 'pinctrl-[0-9]+'
arch/arm64/boot/dts/rockchip/px30-evb.dt.yaml: vop@ff460000:
'power-domains', 'rockchip,grf'
do not match any of the regexes: 'pinctrl-[0-9]+'

'rockchip,grf' is not used by the Rockchip VOP driver,
so remove it from 'vop' nodes in 'px30.dtsi'.

make ARCH=arm64 dtbs_check
DT_SCHEMA_FILES=Documentation/devicetree/bindings/display/
rockchip/rockchip-vop.yaml

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/20200309081600.3887-1-jbx6244@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>