gro: Fix vlan/netpoll check again

Jarek Poplawski pointed out that my previous fix is broken for
VLAN+netpoll as if netpoll is enabled we'd end up in the normal
receive path instead of the VLAN receive path.

This patch fixes it by calling the VLAN receive hook.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>