IB/ipath: Fix IRQ for PCI Express HCAs

Commit 51f65ebc ("IB/ipath - program intconfig register using new HT
irq hook"), which fixed interrupts for HyperTransport HCAs, broke PCI
Express HCAs, because for those HCAs, the driver uses the value of
pdev->irq before pci_enable_msi() and ends up getting a totally bogus
IRQ number.  Fix this by using the value of pdev->irq after
pci_enable_msi().

Signed-off-by: Roland Dreier <rolandd@cisco.com>