net: lan743x: Fix to use multiqueue start/stop APIs

- Fix to use multiqueue start/stop APIs
 - Change to return NETDEV_TX_BUSY instead of holding the TX skb when busy
 - Increase Tx ring size to 128 to address performance issues in some platforms
 - Use NAPI_POLL_WEIGHT for Tx Napi handler instead of ring dependent value
 - Use multiqueue to register 4 Rx channels

Signed-off-by: Raju Lakkaraju <Raju.Lakkaraju@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>