arm64: dts: renesas: white-hawk-cpu: Fix missing serial console pin control

arm64: dts: renesas: white-hawk-cpu: Fix missing serial console pin control

[ Upstream commit fc67495680f60e88bb8ca43421c1dd628928d581 ]

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: 7a8d590de8132853 ("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
Signed-off-by: Sasha Levin <sashal@kernel.org>