6lowpan: make lowpan_cb static

CC: Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: linux-zigbee-devel@lists.sourceforge.net
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ieee802154/reassembly.c b/net/ieee802154/reassembly.c
index 132b65b..6f1428c 100644
--- a/net/ieee802154/reassembly.c
+++ b/net/ieee802154/reassembly.c
@@ -36,7 +36,7 @@
 	u8 d_offset;
 };
 
-struct lowpan_frag_info *lowpan_cb(struct sk_buff *skb)
+static struct lowpan_frag_info *lowpan_cb(struct sk_buff *skb)
 {
 	return (struct lowpan_frag_info *)skb->cb;
 }