arm: mvebu: turris_mox: fix PCIe ranges in device tree

Use the new a3700_fdt_fix_pcie_regions function in turris_mox.c so that
MOX boards with 4 GB RAM are fully supported.

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