[PATCH] xen/9pfs: mark expected switch fall-through in xen_9pfs_front_changed

["Gustavo A. R. Silva" <garsilva@embeddedor.com>]

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Notice that in this particular case, I placed the "fall through" comment
on its own line, which is what GCC is expecting to find.

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
---
This code was tested by compilation only (GCC 7.2.0 was used).

 net/9p/trans_xen.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index 6ad3e04..7ec5df9 100644
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -510,7 +510,8 @@ static void xen_9pfs_front_changed(struct xenbus_device *dev,
 	case XenbusStateClosed:
 		if (dev->state == XenbusStateClosed)
 			break;
-		/* Missed the backend's CLOSING state -- fallthrough */
+		/* Missed the backend's CLOSING state */
+		/* fall through */
 	case XenbusStateClosing:
 		xenbus_frontend_closed(dev);
 		break;
-- 
2.7.4