[NET]: Fix setsockopt locking bug

On Sparc, SO_DONTLINGER support resulted in sock_reset_flag being 
called without lock_sock().
Signed-off-by: Kyle Moffett <mrmacman_g4@mac.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/sock.c

@@ -206,9 +206,10 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 	 */
 
 #ifdef SO_DONTLINGER		/* Compatibility item... */
-	switch (optname) {
-		case SO_DONTLINGER:
+	if (optname == SO_DONTLINGER) {
+		lock_sock(sk);
 		sock_reset_flag(sk, SOCK_LINGER);
+		release_sock(sk);
 		return 0;
 	}
 #endif