pci: irq_state vmstate breakage

Code for saving irq_state got vm_state
macros wrong, passing in the wrong parameter.
As a result, we both saved a wrong value
and restored it to a wrong offset.

This leads to device and bus irq counts getting
out of sync, which in turn leads to interrupts getting lost or
never cleared, such as
https://bugzilla.redhat.com/show_bug.cgi?id=588133

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Juan Quintela <quintela@redhat.com>
