vmxnet3: do not stop tx queues after netif_device_detach()

The netif_device_detach() conditionally stops all tx queues if the queues
are running. There is no need to call netif_tx_stop_all_queues() again.

Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>