batman-adv: Use 'fallthrough' pseudo keyword

The usage of the '/* fall through */' comments in switches are no longer
marked as non-deprecated variant of implicit fall throughs for switch
statements. The commit 294f69e6 ("compiler_attributes.h: Add
'fallthrough' pseudo keyword for switch/case use") introduced a replacement
keyword which should be used instead.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

net/batman-adv/multicast.c

@@ -1421,7 +1421,7 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
 		if (*orig)
 			return BATADV_FORW_SINGLE;
 
-		/* fall through */
+		fallthrough;
 	case 0:
 		return BATADV_FORW_NONE;
 	default:

net/batman-adv/soft-interface.c

@@ -230,7 +230,7 @@ static netdev_tx_t batadv_interface_tx(struct sk_buff *skb,
 			break;
 		}
 
-		/* fall through */
+		fallthrough;
 	case ETH_P_BATMAN:
 		goto dropped;
 	}
@@ -455,7 +455,7 @@ void batadv_interface_rx(struct net_device *soft_iface,
 		if (vhdr->h_vlan_encapsulated_proto != htons(ETH_P_BATMAN))
 			break;
 
-		/* fall through */
+		fallthrough;
 	case ETH_P_BATMAN:
 		goto dropped;
 	}