ARM: dts: aspeed: Add Mowgli BMC platform

The Mowgli BMC is an ASPEED ast2500 based BMC that is part of an
OpenPower Power9 server.

Signed-off-by: Ben Pai <Ben_Pai@wistron.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20200909090818.24021-1-ben_pai@wistron.com


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