net: ethernet: ti: ale: use devm_kzalloc in cpsw_ale_create()

Use cpsw_ale_create in cpsw_ale_create(). This also makes
cpsw_ale_destroy() function nop, so remove it.

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