net: stmmac: adding multiple napi mechanism

This patch adds the napi variable to the stmmac_rx_queue
structure and forces that operations like netif_queue_stopped,
netif_wake_queue, netif_stop_queue, netdev_reset_queue and
netdev_sent_queue be made by queue.

Signed-off-by: Joao Pinto <jpinto@synopsys.com>
Tested-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>