ARM: dts: nuvoton,wpcm450-supermicro-x9sci-ln4f: Add GPIO line names

ARM: dts: nuvoton,wpcm450-supermicro-x9sci-ln4f: Add GPIO line names

To make gpioinfo output more useful and enable gpiofind usage, add line
names for GPIOs where the function is known.

This patch follows the naming convention defined for OpenBMC, as much as
possible:

  https://github.com/openbmc/docs/blob/master/designs/device-tree-gpio-naming.md

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20221101102916.440526-1-j.neuschaefer@gmx.net
Signed-off-by: Joel Stanley <joel@jms.id.au>