9p: Fix comment on smp_wmb

The previous comment misled me into thinking the barrier wasn't needed
at all.

Link: http://lkml.kernel.org/r/20180711210225.19730-2-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>

net/9p/client.c

@@ -448,7 +448,7 @@ void p9_client_cb(struct p9_client *c, struct p9_req_t *req, int status)
 
 	/*
 	 * This barrier is needed to make sure any change made to req before
-	 * the other thread wakes up will indeed be seen by the waiting side.
+	 * the status change is visible to another thread
 	 */
 	smp_wmb();
 	req->status = status;