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/drivers/atm/firestream.c b/drivers/atm/firestream.c
index b119640..cd5049a 100644
--- a/drivers/atm/firestream.c
+++ b/drivers/atm/firestream.c
@@ -1244,7 +1244,7 @@
 
 
 static int fs_setsockopt(struct atm_vcc *vcc,int level,int optname,
-			 void __user *optval,int optlen)
+			 void __user *optval,unsigned int optlen)
 {
 	func_enter ();
 	func_exit ();