vhost_kern: add vhost_msg_v2 bindings
vhost_kern: add vhost_msg_v2 bindings

Add structs and tests for the C 'struct vhost_msg_v2' type supported
by vhost-kern.

Signed-off-by: Stefano Garzarella <6f3dd2004310421c0dda1107f4857e62a774d5df@redhat.com>

rust-vmm/vhost