fiq_fsm: Implement hack for Split Interrupt transactions

Hubs aren't too picky about which endpoint we send Control type split
transactions to. By treating Interrupt transfers as Control, it is
possible to use the non-periodic queue in the OTG core as well as the
non-periodic FIFOs in the hub itself. This massively reduces the
microframe exclusivity/contention that periodic split transactions
otherwise have to enforce.

It goes without saying that this is a fairly egregious USB specification
violation, but it works.

Original idea by Hans Petter Selasky @ FreeBSD.org.