src/sys/dev/virtio/console, branch stable/10

src/sys/dev/virtio/console, branch stable/10 FreeBSD source tree MFC r273515, r274055, r274063, r274215, r274065, r274502: 2014-11-29T22:48:40+00:00 Bryan Venteicher bryanv@FreeBSD.org 2014-11-29T22:48:40+00:00 213d6f31aaf5d2939064b7c5f27f9c3939be3336 Add VirtIO console driver.

Add VirtIO console driver.