NFS: Mark expected switch fall-throughs

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

Warning level 2 was used: -Wimplicit-fallthrough=2

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/fs/nfs/nfs4idmap.c b/fs/nfs/nfs4idmap.c
index cf72169..3f23b68 100644
--- a/fs/nfs/nfs4idmap.c
+++ b/fs/nfs/nfs4idmap.c
@@ -506,6 +506,7 @@
 	switch (token) {
 	case Opt_find_uid:
 		im->im_type = IDMAP_TYPE_USER;
+		/* Fall through */
 	case Opt_find_gid:
 		im->im_conv = IDMAP_CONV_NAMETOID;
 		ret = match_strlcpy(im->im_name, &substr, IDMAP_NAMESZ);
@@ -513,6 +514,7 @@
 
 	case Opt_find_user:
 		im->im_type = IDMAP_TYPE_USER;
+		/* Fall through */
 	case Opt_find_group:
 		im->im_conv = IDMAP_CONV_IDTONAME;
 		ret = match_int(&substr, &im->im_id);