ASP 2.2 improves power savings during low power modes.

A new register was added to toggle to a slower clock during low
power modes.

EEE was broken for ASP 2.0/2.1. A HW workaround was added for
ASP 2.2 that requires toggling a chicken bit.
Signed-off-by: Justin Chen <justin.chen@broadcom.com>
Acked-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>