PCI: mediatek: Use PCI domain to handle ports detection

Use of_get_pci_domain_nr() to get the pci domain.

If the "linux,pci-domain" property is present, we assume that the PCIe
bridge is an individual bridge, hence we only need to parse one port.

Link: https://lore.kernel.org/r/20210823032800.1660-5-chuanjia.liu@mediatek.com


Signed-off-by: Chuanjia Liu <chuanjia.liu@mediatek.com>
[lorenzo.pieralisi@arm.com: commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Ryder Lee <ryder.lee@mediatek.com>