net: ethernet: ti: ale: disable ale from stop()

ALE is enabled from cpsw_ale_start() now, but disabled only from
cpsw_ale_destroy() which introduces inconsitance as cpsw_ale_start() is
called when netif[s] is opened, but cpsw_ale_destroy() is called when
driver is removed. Hence, move ALE disabling in cpsw_ale_stop().

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>