ARM: dts: wpcm450: Add pinmux information to UART0

UART0 always uses the same pins, so lets add the pinctrl information to
the common devicetree for WPCM450.

UART1 has different connection options, so I'm not adding the pinctrl
properties there.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20220129115228.2257310-10-j.neuschaefer@gmx.net


Signed-off-by: Joel Stanley <joel@jms.id.au>