PCI: xilinx-nwl: Remove nwl_pcie_enable_msi() unused bus parameter

The nwl_pcie_enable_msi() second parameter (ie "bus") is unused and creates
a fake dependency on the struct pci_bus that need not exist.

Remove it.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Bharat Kumar Gogada <bharat.kumar.gogada@xilinx.com>