Smack: Mark expected switch fall-through

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

Notice that in this particular case, I replaced "No break" with a
proper "Fall through" annotation, which is what GCC is expecting
to find.

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

Addresses-Coverity-ID: 115051 ("Missing break in switch")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

security/smack/smack_lsm.c

@@ -3474,7 +3474,7 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
 		 */
 		final = &smack_known_star;
 		/*
-		 * No break.
+		 * Fall through.
 		 *
 		 * If a smack value has been set we want to use it,
 		 * but since tmpfs isn't giving us the opportunity