ARM: dts: wpcm450: Add pin functions

As done in nuvoton-common-npcm7xx.dtsi, this patch adds pinmux nodes for
all pin functions to nuvoton-wpcm450.dtsi.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20220129115228.2257310-8-j.neuschaefer@gmx.net


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