axnet_cs: reduce delay time at ei_rx_overrun

axnet_cs:
    mdelay of 10ms is too long at ei_rx_overrun.
    It should be reduced to 2ms.

Signed-off-by: Ken Kawasaki <ken_kawasaki@spring.nifty.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>