Remove dev/virtio/virtio.h include from BERI VirtIO

This header file contains prototypes and defines that only make
sense to the guest VirtIO device drivers.

Reviewed by:	br


git-svn-id: svn+ssh://svn.freebsd.org/base/head@276354 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f