arm: mvebu: add basic address decoding support to Armada 370/XP

This commit adds basic support for address decoding configuration for
the Armada 370 and Armada XP SoCs, re-using the infrastructure
provided in plat-orion.

For now, only a BootROM window is configured on Armada XP, which is
needed to get the non-boot CPUs started and is therefore a requirement
for SMP support.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>