net/9p/trans_virtio.c: fix some spell mistakes in comments

Fix spelling mistake in comments of p9_virtio_zc_request().

Link: http://lkml.kernel.org/r/5B4EB7D9.9010108@huawei.com


Signed-off-by: Jun Piao <piaojun@huawei.com>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>