net: gemini: Fix missing free_netdev() in error path of gemini_ethernet_port_probe()

Replace alloc_etherdev_mq with devm_alloc_etherdev_mqs. In this way,
when probe fails, netdev can be freed automatically.

Fixes: 4d5ae32f

 ("net: ethernet: Add a driver for Gemini gigabit ethernet")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>