inet: Use fallthrough;

Convert the various uses of fallthrough comments to fallthrough;

Done via script
Link: https://lore.kernel.org/lkml/b56602fcf79f849e733e7b521bb0e17895d390fa.1582230379.git.joe@perches.com/

And by hand:

net/ipv6/ip6_fib.c has a fallthrough comment outside of an #ifdef block
that causes gcc to emit a warning if converted in-place.

So move the new fallthrough; inside the containing #ifdef/#endif too.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

@@ -2865,7 +2865,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una,
 		      (*ack_flag & FLAG_LOST_RETRANS)))
 			return;
 		/* Change state if cwnd is undone or retransmits are lost */
-		/* fall through */
+		fallthrough;
 	default:
 		if (tcp_is_reno(tp)) {
 			if (flag & FLAG_SND_UNA_ADVANCED)
@@ -6367,7 +6367,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 				mptcp_incoming_options(sk, skb, &tp->rx_opt);
 			break;
 		}
-		/* fall through */
+		fallthrough;
 	case TCP_FIN_WAIT1:
 	case TCP_FIN_WAIT2:
 		/* RFC 793 says to queue data in these states,
@@ -6382,7 +6382,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 				return 1;
 			}
 		}
-		/* Fall through */
+		fallthrough;
 	case TCP_ESTABLISHED:
 		tcp_data_queue(sk, skb);
 		queued = 1;