arm64: dts: rockchip: remove bus-width from mmc nodes in px30 dts files

'bus-width' has been added to px30.dtsi mmc nodes, so now it can be
removed from the dts files that include it.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/20200715070954.1992-1-jbx6244@gmail.com


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