[IA64] remove "pci=routeirq" option

Remove "pci=routeirq" option for ia64.  This was a workaround
after ACPI IRQ routing was changed from "all at boot for everything
in _PRT" to "do it when the device is enabled" in case there were
drivers that didn't use pci_enable_device().

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>