igbvf: do not modify tx_queue_len on link speed change

Previously the driver tweaked txqueuelen to avoid false Tx hang reports seen at half duplex.
This had the effect of overriding user set values on link change/reset. Testing shows that
adjusting only the timeout factor is sufficient to prevent Tx hang reports at half duplex.

Based on e1000e patch by Franco Fichtner <[e-mail]>

CC: Franco Fichtner <[e-mail]>
Signed-off-by: Emil Tantilov <[e-mail]>
Signed-off-by: Jeff Kirsher <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/igbvf/igbvf.h

···
 	struct igbvf_ring *tx_ring /* One per active queue */
 	____cacheline_aligned_in_smp;
 
-	unsigned long tx_queue_len;
 	unsigned int restart_queue;
 	u32 txd_cmd;
 

drivers/net/igbvf/netdev.c

···
 
 	/* enable Report Status bit */
 	adapter->txd_cmd |= E1000_ADVTXD_DCMD_RS;
-
-	adapter->tx_queue_len = adapter->netdev->tx_queue_len;
 }
 
 /**
···
 
 	del_timer_sync(&adapter->watchdog_timer);
 
-	netdev->tx_queue_len = adapter->tx_queue_len;
 	netif_carrier_off(netdev);
 
 	/* record the stats before reset*/
···
 			                          &adapter->link_duplex);
 			igbvf_print_link_info(adapter);
 
-			/*
-			 * tweak tx_queue_len according to speed/duplex
-			 * and adjust the timeout factor
-			 */
-			netdev->tx_queue_len = adapter->tx_queue_len;
+			/* adjust timeout factor according to speed/duplex */
 			adapter->tx_timeout_factor = 1;
 			switch (adapter->link_speed) {
 			case SPEED_10:
 				txb2b = 0;
-				netdev->tx_queue_len = 10;
 				adapter->tx_timeout_factor = 16;
 				break;
 			case SPEED_100:
 				txb2b = 0;
-				netdev->tx_queue_len = 100;
 				/* maybe add some timeout factor ? */
 				break;
 			}