The pin control description for the serial console was added, but not
enabled, due to missing pinctrl properties in the serial port device
node.

Fixes: 7a8d590d ("arm64: dts: renesas: white-hawk-cpu: Add serial port pin control")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/8a51516581cd71ecbfa174af9c7cebad1fc83c5b.1702459865.git.geert+renesas@glider.be