PCI: mediatek: Enlarge PCIe2AHB window size to support 4GB DRAM

The PCIE_AXI_WINDOW0 register defines the inbound window size for
requests coming from PCI endpoints. Requests outside of this window will
be treated as unsupported requests.

Enlarge this window size from 2^31 to 2^33 to support a 8GB address
space (which gives endpoints DMA access to full 4GB DRAM address range
- physical DRAM starts at 0x40000000).

Reported-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Honghui Zhang <honghui.zhang@mediatek.com>
[lorenzo.pieralisi@arm.com: updated commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>