arm64: mvebu: a37xx: add device-tree fixer for PCIe regions

In case when ARM Trusted Firmware changes the default address of PCIe
regions (which can be done for devices with 4 GB RAM to maximize the
amount of RAM the device can use) we add code that looks at how ATF
changed the PCIe windows in the CPU Address Decoder and changes given
device-tree blob accordingly.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>