net: ethernet: ti: ale: am65: add support for default thread cfg

Add support for default thread configuration for AM65x CPSW NUSS ALE to
allow route all ingress packets to one default RX UDMA flow.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Tested-by: Murali Karicheri <m-karicheri2@ti.com>
Tested-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>