net: mv643xx_eth: Add GRO support

This patch adds GRO support to mv643xx_eth by making it invoke
napi_gro_receive instead of netif_receive_skb.

Signed-off-by: Soeren Moch <smoch@web.de>
Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>