ARM: platform support for Nuvoton WPCM450

The Nuvoton WPCM450 BMC is an older chip based on the ARM926 CPU core
that remains in use on Supermicro X9 server boards among others. Support
gets added for a particular server board using this SoC along with the
basic platform bringup.

As the platform is a predecessor to the npcm7xx platform we already
support, it is added to the same directory, despite using a different
name. It also seems to be related to the older w90x900/nuc9xx platform
that was removed last year.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>