virtio: get rid of redundant VIRTIO_ID_9P definition

VIRTIO_ID_9P is already defined in include/linux/virtio_9p.h
so use that definition instead.

Signed-off-by: Fernando Luis Vazquez Cao <[e-mail]>
Signed-off-by: Rusty Russell <[e-mail]>
Cc: Eric Van Hensbergen <[e-mail]>

net/9p/trans_virtio.c

···
 	}
 }
 
-#define VIRTIO_ID_9P 9
-
 static struct virtio_device_id id_table[] = {
 	{ VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
 	{ 0 },