tg3: tg3_reset_task() needs to use rtnl_lock to synchronize

Currently tg3_reset_task() uses only tp->lock for synchronizing with code
paths like tg3_open() etc. But since tp->lock is released before doing
synchronize_irq(), rtnl_lock should be taken in tg3_reset_task() to
synchronize it with other code paths.

Reported-by: Peter Hurley <peter@hurleysoftware.com>
Tested-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Prashant Sreedharan <prashant@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/tg3.c

@@ -11103,11 +11103,13 @@ static void tg3_reset_task(struct work_struct *work)
 	struct tg3 *tp = container_of(work, struct tg3, reset_task);
 	int err;
 
+	rtnl_lock();
 	tg3_full_lock(tp, 0);
 
 	if (!netif_running(tp->dev)) {
 		tg3_flag_clear(tp, RESET_TASK_PENDING);
 		tg3_full_unlock(tp);
+		rtnl_unlock();
 		return;
 	}
 
@@ -11140,6 +11142,7 @@ out:
 		tg3_phy_start(tp);
 
 	tg3_flag_clear(tp, RESET_TASK_PENDING);
+	rtnl_unlock();
 }
 
 static int tg3_request_irq(struct tg3 *tp, int irq_num)