arm64: dts: rockchip: move px30-evb console output to uart 5

The px30-evb exposes uart2 through a uart-to-usb converter on the board
but these pins are shared with the sdmmc controller. With both activated
this results in a race condition depending in the probe order.
Whichever of the two probes first will break the other peripheral.

The px30-evb also exposes uart5 through pin its pin headers, so it's way
saner to use these pins for serial output and keep the sdmmc working in
all cases.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20190917082659.25549-7-heiko@sntech.de