6166 fix MSI-X support in virtio driver
Reviewed by: Daniel Kimmel <dan.kimmel@delphix.com>
Reviewed by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Approved by: Robert Mustacchi <rm@joyent.com>

1562 Integrate the virtio core module
Reviewed by: Dmitry Yusupov <Dmitry.Yusupov@nexenta.com>
Reviewed by: Gordon Ross <gordon.w.ross@gmail.com>
Approved by: Garrett D'Amore <garrett@damore.org>