6lowpan: fix a small formatting issue

This formatting issue was introduced with commit
d4ac32365dcbfd341a87eae444c26679f889249a

Signed-off-by: Tony Cheneau <tony.cheneau@amnesiak.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ieee802154/6lowpan.c

@@ -104,7 +104,7 @@ static const u8 lowpan_llprefix[] = {0xfe, 0x80};
 struct lowpan_dev_info {
 	struct net_device	*real_dev; /* real WPAN device ptr */
 	struct mutex		dev_list_mtx; /* mutex for list ops */
-	unsigned short fragment_tag;
+	unsigned short		fragment_tag;
 };
 
 struct lowpan_dev_record {