arm: a37xx: pci: Fix a3700_fdt_fix_pcie_regions() function

Current version of this function uses a lot of incorrect assumptions about
the `ranges` DT property:

 * parent(#address-cells) == 2
 * #size-cells == 2
 * number of entries == 2
 * address size of first entry == 0x1000000
 * second child address entry == base + 0x1000000

Trying to increase PCIe MEM space to more than 16 MiB leads to an overlap
with PCIe IO space, and trying to define additional MEM space (as a third
entry in the `ranges` DT property) causes U-Boot to crash when booting the
kernel.

  ## Flattened Device Tree blob at 04f00000
     Booting using the fdt blob at 0x4f00000
     Loading Device Tree to 000000001fb01000, end 000000001fb08f12 ... OK
  ERROR: board-specific fdt fixup failed: <unknown error>
   - must RESET the board to recover.

Fix a3700_fdt_fix_pcie_regions() to properly parse and update all addresses
in the `ranges` property according to
https://elinux.org/Device_Tree_Usage#PCI_Address_Translation



Now it is possible to increase PCIe MEM space from 16 MiB to maximal value
of 127 MiB.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Marek Behún <marek.behun@nic.cz>
Fixes: cb2ddb29 ("arm64: mvebu: a37xx: add device-tree fixer for PCIe regions")
Reviewed-by: Stefan Roese <sr@denx.de>