sctp: fix sctp_setsockopt_autoclose compile warning

Fix the following warning, when building on 64 bits:

net/sctp/socket.c:2091: warning: large integer implicitly
                        truncated to unsigned type
Signed-off-by: Andrei Pelinescu-Onciul <andrei@iptel.org>
Acked-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/socket.c

@@ -2088,7 +2088,7 @@ static int sctp_setsockopt_autoclose(struct sock *sk, char __user *optval,
 		return -EFAULT;
 	/* make sure it won't exceed MAX_SCHEDULE_TIMEOUT */
 	if (sp->autoclose > (MAX_SCHEDULE_TIMEOUT / HZ) )
-		sp->autoclose = MAX_SCHEDULE_TIMEOUT / HZ ;
+		sp->autoclose = (__u32)(MAX_SCHEDULE_TIMEOUT / HZ) ;
 
 	return 0;
 }