r8169: fix interrupt number after adding support for MSI-X interrupts

In case of MSI-X the interrupt number may differ from pcidev->irq.
Fix this by using pci_irq_vector().

Fixes: 6c6aa15f ("r8169: improve interrupt handling")
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>