ARM: dts: aspeed: Add Facebook Wedge400 BMC

Add initial version of device tree for Facebook Wedge400 (AST2500) BMC.

Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20200824211948.12852-6-rentao.bupt@gmail.com


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