gve: Correct SKB queue index validation.

[ Upstream commit fbd4a28b ]

SKBs with skb_get_queue_mapping(skb) == tx_cfg.num_queues should also be
considered invalid.

Fixes: f5cedc84 ("gve: Add transmit and receive support")
Signed-off-by: David Awogbemila <awogbemila@google.com>
Acked-by: Willem de Brujin <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>