PCI: xgene: Rename xgene_pcie_port to xgene_pcie

Rename struct xgene_pcie_port to xgene_pcie to match the convention of
<driver>_pcie. No functional change intended.

Link: https://lore.kernel.org/r/20211223011054.1227810-22-helgaas@kernel.org


Signed-off-by: Fan Fei <ffclaire1224@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Toan Le <toan@os.amperecomputing.com>