[NET]: Fix comparisons of unsigned < 0.

Recent gcc versions emit warnings when unsigned variables are
compared < 0 or >= 0.

Signed-off-by: Bill Nottingham <notting@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/probe.c b/net/dccp/probe.c
index 1f5e3ba..43a3adb 100644
--- a/net/dccp/probe.c
+++ b/net/dccp/probe.c
@@ -128,7 +128,7 @@
 	int error = 0, cnt = 0;
 	unsigned char *tbuf;
 
-	if (!buf || len < 0)
+	if (!buf)
 		return -EINVAL;
 
 	if (len == 0)