9p/fsdev: remove obsolete references to virtio

Most of the 9p code is now virtio agnostic. This patch does a final cleanup:
- drop references to Virtio from the header comments
- fix includes

Also drop a couple of leading empty lines while here.

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>

fsdev/qemu-fsdev-opts.c

@@ -1,5 +1,5 @@
 /*
- * Virtio 9p
+ * 9p
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or
  * later.  See the COPYING file in the top-level directory.