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/llc/af_llc.c b/net/llc/af_llc.c
index c45eee1..7aa4fd1 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -973,7 +973,7 @@
  *	Set various connection specific parameters.
  */
 static int llc_ui_setsockopt(struct socket *sock, int level, int optname,
-			     char __user *optval, int optlen)
+			     char __user *optval, unsigned int optlen)
 {
 	struct sock *sk = sock->sk;
 	struct llc_sock *llc = llc_sk(sk);