e1000: remove set but not used variable 'txb2b'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/ethernet/intel/e1000/e1000_main.c: In function 'e1000_watchdog':
drivers/net/ethernet/intel/e1000/e1000_main.c:2436:9: warning:
 variable 'txb2b' set but not used [-Wunused-but-set-variable]
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/intel/e1000/e1000_main.c

@@ -2433,7 +2433,6 @@ static void e1000_watchdog(struct work_struct *work)
 	if (link) {
 		if (!netif_carrier_ok(netdev)) {
 			u32 ctrl;
-			bool txb2b = true;
 			/* update snapshot of PHY registers on LSC */
 			e1000_get_speed_and_duplex(hw,
 						   &adapter->link_speed,
@@ -2455,11 +2454,9 @@ static void e1000_watchdog(struct work_struct *work)
 			adapter->tx_timeout_factor = 1;
 			switch (adapter->link_speed) {
 			case SPEED_10:
-				txb2b = false;
 				adapter->tx_timeout_factor = 16;
 				break;
 			case SPEED_100:
-				txb2b = false;
 				/* maybe add some timeout factor ? */
 				break;
 			}