net/xfrm: use kmemdup rather than duplicating its implementation

The patch was generated using fixed coccinelle semantic patch
scripts/coccinelle/api/memdup.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2014320Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/xfrm/xfrm_user.c

@@ -925,12 +925,10 @@ static int xfrm_dump_sa(struct sk_buff *skb, struct netlink_callback *cb)
 			return err;
 
 		if (attrs[XFRMA_ADDRESS_FILTER]) {
-			filter = kmalloc(sizeof(*filter), GFP_KERNEL);
+			filter = kmemdup(nla_data(attrs[XFRMA_ADDRESS_FILTER]),
+					 sizeof(*filter), GFP_KERNEL);
 			if (filter == NULL)
 				return -ENOMEM;
-
-			memcpy(filter, nla_data(attrs[XFRMA_ADDRESS_FILTER]),
-			       sizeof(*filter));
 		}
 
 		if (attrs[XFRMA_PROTO])