ARM: dts: aspeed: Add device tree for Ampere's Mt. Jade BMC

The Mt. Jade BMC is an ASPEED AST2500-based BMC for the Mt. Jade
hardware reference platform with Ampere's Altra Processor Family.

Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
Signed-off-by: Phong Vo <phong@os.amperecomputing.com>
Signed-off-by: Thang Q. Nguyen <thang@os.amperecomputing.com>
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20201208043700.23098-3-quan@os.amperecomputing.com


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