PCI: xilinx: Rename xilinx_pcie_port to xilinx_pcie

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

Link: https://lore.kernel.org/r/20211223011054.1227810-23-helgaas@kernel.org


Signed-off-by: Fan Fei <ffclaire1224@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>