net: marvell: always set skb_shared_info in mvneta_swbm_add_rx_fragment

Always set skb_shared_info data structure in mvneta_swbm_add_rx_fragment
routine even if the fragment contains only the ethernet FCS.

Fixes: 039fbc47 ("net: mvneta: alloc skb_shared_info on the mvneta_rx_swbm stack")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>