ARM: Add wpcm450_defconfig for Nuvoton WPCM450

This defconfig aims to offer a reasonable set of defaults for all
systems running on a Nuvoton WPCM450 chip.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20230129041547.942335-1-j.neuschaefer@gmx.net
Signed-off-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20230201051534.1005847-1-joel@jms.id.au
Signed-off-by: Arnd Bergmann <arnd@arndb.de>