arm: a37xx: Remap IO space to bus address 0x0

Remap PCI I/O space to the bus address 0x0 in the Armada 37xx device-tree
in order to support legacy I/O port based cards which have hardcoded I/O
ports in low address space.

Some legacy PCI I/O based cards do not support 32-bit I/O addressing.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>