PCI: mediatek: Allow building for ARCH_AIROHA

Allow selecting the pcie-mediatek driver if ARCH_AIROHA is set, because the
Airoha EN7523 SoC uses the same controller as MT7622.

The driver itself is not modified. The PCIe controller DT node should use
mediatek,mt7622-pcie after airoha,en7523-pcie.

Link: https://lore.kernel.org/r/20220615125335.96089-2-nbd@nbd.name


Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>