Pull up following revision(s) (requested by knakahara in ticket #658):
sys/arch/x86/x86/intr.c: revision 1.124
Fix "intrctl list" causes panic while attaching MSI/MSI-X devices.
When there are devices which is already pci_intr_alloc'ed, however is not
established yet, "intrctl list" causes panic. E.g.
    # while true; do intrctl list > /dev/null ; done&
    # drvctl -d ixg0 && drvctl -r pci0
And add some KASSERTMSG to similar but not the same code.
Pointed out by msaitoh@n.o.
XXX pullup-8

(martin)