Bug 870422 (follow-up): fix cpu abort in `goldfish_device_set_irq`.

The 2nd param of `goldfish_device_set_irq()` is the nth IRQ owned by
the device, not the global IRQ number.
Merge pull request #32 from vicamo/bugzilla/870422/follow-up

Bug 870422 (follow-up): fix cpu abort in `goldfish_device_set_irq`. r=me