Fix array out of bound panic introduced in r306219.

As I see, different NICs in different configurations may have different
numbers of TX and RX queues. The code was assuming 1:1 mapping between
event queues (interrupts) and TX/RX queues. Since number of interrupts
is set to maximum of TX and RX queues, when those two are different, the
system is doomed.

I have no documentation or deep knowledge about this hardware, so this
change is based on general observations and code reading. If some of my
guesses are wrong, please do better. I just confirmed HP NC550SFP NICs
are working now.

MFC after: 2 weeks
Sponsored by: iXsystems, Inc.