PCI: altera: Fix error when INTx is 4

PCI interrupt lines start at 1, not at 0.  So, creates additional one
interrupt when register for irq domain.

Error when PCIe devices have 4 INTx:

  WARNING: CPU: 1 PID: 1 at kernel/irq/irqdomain.c:280
    irq_domain_associate+0x17c/0x1cc()
  error: hwirq 0x4 is too large for dummy

Tested on Ethernet adapter card with multi-functions.

Signed-off-by: Ley Foon Tan <lftan@altera.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>