PCI: mediatek: Use pci_parse_request_of_pci_ranges()

Convert Mediatek host bridge to use the common
pci_parse_request_of_pci_ranges().

Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Andrew Murray <andrew.murray@arm.com>
Cc: Ryder Lee <ryder.lee@mediatek.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: linux-mediatek@lists.infradead.org