ARM: dts: wpcm450-supermicro-x9sci-ln4f: Add SPI flash

Add the BMC firmware flash to the devicetree, so that it can be accessed
from Linux.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20221105185911.1547847-7-j.neuschaefer@gmx.net


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