xfrm6: release dev before returning error

We forget to call dev_put() on error path in xfrm6_fill_dst(),
its caller doesn't handle this.

Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c
index 4ef7bdb..23ed03d 100644
--- a/net/ipv6/xfrm6_policy.c
+++ b/net/ipv6/xfrm6_policy.c
@@ -103,8 +103,10 @@
 	dev_hold(dev);
 
 	xdst->u.rt6.rt6i_idev = in6_dev_get(dev);
-	if (!xdst->u.rt6.rt6i_idev)
+	if (!xdst->u.rt6.rt6i_idev) {
+		dev_put(dev);
 		return -ENODEV;
+	}
 
 	rt6_transfer_peer(&xdst->u.rt6, rt);