net: Make setsockopt() optlen be unsigned.

This provides safety against negative optlen at the type
level instead of depending upon (sometimes non-trivial)
checks against this sprinkled all over the the place, in
each and every implementation.

Based upon work done by Arjan van de Ven and feedback
from Linus Torvalds.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index e8254e8..e6d9abf 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -1658,7 +1658,7 @@
  */
 
 static int setsockopt(struct socket *sock,
-		      int lvl, int opt, char __user *ov, int ol)
+		      int lvl, int opt, char __user *ov, unsigned int ol)
 {
 	struct sock *sk = sock->sk;
 	struct tipc_port *tport = tipc_sk_port(sk);