net/virtio: fix memory leak on failure

In function eth_virtio_dev_init(), dynamic memory stored
in "eth_dev->data->mac_addrs" variable and it is not freed
when function return,
this is a possible memory leak.

Fixes: 8ced1542f7a3 ("net/virtio: eth_dev->data->mac_addrs is not freed")
Cc: stable@dpdk.org
Signed-off-by: Pengzhen Liu <liupengzhen3@huawei.com>
Acked-by: Yuanhan Liu <yliu@fridaylinux.org>