xfrm: Fix xfrm_state_migrate leak

xfrm_state_migrate calls kfree instead of xfrm_state_put to free
a failed state. According to git commit 553f9118 this can cause
memory leaks.
Signed-off-by: Thomas Egerer <thomas.egerer@secunet.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/xfrm/xfrm_state.c

@@ -1268,7 +1268,7 @@ struct xfrm_state * xfrm_state_migrate(struct xfrm_state *x,
 
 	return xc;
 error:
-	kfree(xc);
+	xfrm_state_put(xc);
 	return NULL;
 }
 EXPORT_SYMBOL(xfrm_state_migrate);