If tx timeout event occur, kernel will call rtl8139_tx_timeout_task() to reset
hardware. But in this function, driver does not stop tx and rx function before
reset hardware, that will cause system hang.

In this patch, add stop tx and rx function before reset hardware.
Signed-off-by: Chunhao Lin <hau@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>