ARM: dts: aspeed: Add Qanta Q71L BMC machine

The Qanta Q71L BMC is an ASPEED ast2400 based BMC that is part of a
Qanta x86 server.

This adds the device tree description for most upstream components. It
is a squashed commit from the OpenBMC kernel tree.

Signed-off-by: Peter Hanson <peterh@google.com>
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Patrick Venture <venture@google.com>
Signed-off-by: Rick Altherr <raltherr@google.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>