netxen: fix msi irq setup

The pdev->irq was not saved in netxen_adapter, causing request_irq()
with invalid irq number.

This was broken in commit be339aee
("netxen: fix irq tear down and msix leak.").

Signed-off-by: Dhananjay Phadke <dhananjay@netxen.com>
Signed-off-by: David S. Miller <davem@davemloft.net>