MFC r331355:
Clear old MSIX IRQ numbers in the LinuxKPI.

When disabling the MSIX IRQ vectors for a PCI device through the
LinuxKPI, make sure any old MSIX IRQ numbers are no longer visible to
the linux_pci_find_irq_dev() function else IRQs can be requested from
the wrong PCI device.

Sponsored by: Mellanox Technologies