The virtio headers have changed recently:

 5b1bf7cb virtio_ring: let virtqueue_{kick()/notify()} return a bool
 46f9c2b9

 virtio_ring: change host notification API

Update the internal copies to fix the build of virtio_test:

  cc -g -O2 -Wall -I. -I ../../usr/include/ -Wno-pointer-sign
    -fno-strict-overflow -fno-strict-aliasing -fno-common -MMD -U_FORTIFY_SOURCE
    -c -o virtio_test.o virtio_test.c
  In file included from virtio_test.c:15:0:
  ./linux/virtio.h:76:19: error: conflicting types for ‘vring_new_virtqueue’
   struct virtqueue *vring_new_virtqueue(unsigned int index,
                     ^
  In file included from ./linux/virtio_ring.h:1:0,
                   from ../../usr/include/linux/vhost.h:17,
                   from virtio_test.c:14:
  ./linux/../../../include/linux/virtio_ring.h:68:19: note: previous
  declaration of ‘vring_new_virtqueue’ was here
   struct virtqueue *vring_new_virtqueue(unsigned int index,
  virtio_test.c: In function ‘vq_info_add’:
  virtio_test.c:103:12: warning: passing argument 7 of ‘vring_new_virtqueue’
  from incompatible pointer type [enabled by default]
              vq_notify, vq_callback, "test");
              ^
  In file included from virtio_test.c:15:0:
  ./linux/virtio.h:76:19: note: expected ‘void (*)(struct virtqueue *)’ but
  argument is of type ‘_Bool (*)(struct virtqueue *)’
   struct virtqueue *vring_new_virtqueue(unsigned int index,
                     ^

Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>