bhyve: add NVMe Feature Interrupt Vector Config

This adds support for NVMe Get Features, Interrupt Vector Config
parameter error checking done by the UNH compliance tests.

Fixes UNH Tests 1.6.8 and 5.5.6

Tested by: Jason Tubnor
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D24898