[NET]: Use typesafe inet_twsk() inline function instead of cast.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index bf692c1..7e746c4 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -311,7 +311,7 @@
 	}
 
 	if (sk->sk_state == DCCP_TIME_WAIT) {
-		inet_twsk_put((struct inet_timewait_sock *)sk);
+		inet_twsk_put(inet_twsk(sk));
 		return;
 	}
 
@@ -614,7 +614,7 @@
 			bh_lock_sock(nsk);
 			return nsk;
 		}
-		inet_twsk_put((struct inet_timewait_sock *)nsk);
+		inet_twsk_put(inet_twsk(nsk));
 		return NULL;
 	}
 
@@ -980,7 +980,7 @@
 	goto discard_it;
 
 do_time_wait:
-	inet_twsk_put((struct inet_timewait_sock *)sk);
+	inet_twsk_put(inet_twsk(sk));
 	goto no_dccp_socket;
 }