ARM: npcm: Introduce Nuvoton WPCM450 SoC

The WPCM450 is an older BMC SoC in the Nuvoton NPCM family, originally
marketed as Winbond WPCM450.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20210406120921.2484986-6-j.neuschaefer@gmx.net
Signed-off-by: Joel Stanley <joel@jms.id.au>