bnx2x makes a dangerous use of skb_is_gso_v6().

It should first make sure skb is a gso packet
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Eilon Greenstein <eilong@broadcom.com>
Acked-by: NDmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>