PCI: remove "pci=routeirq" noise from dmesg

The "pci=routeirq" option was added in 2004, and I don't get any valid
reports anymore.  The option is still mentioned in kernel-parameters.txt.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>