ARM: dts: aspeed: Add Ingrasys Zaius BMC machine

Zaius is a POWER9 platform announced at OpenPOWER Summit 2016. This adds
basic DTS support for its AST2500 BMC.

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

Signed-off-by: Xo Wang <xow@google.com>
Signed-off-by: Patrick Venture <venture@google.com>
Signed-off-by: Robert Lippert <rlippert@google.com>
Signed-off-by: Peter Hanson <peterh@google.com>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Rick Altherr <raltherr@google.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>