sis190: add identifier for Atheros AR8021 PHY

Fixes http://bugzilla.kernel.org/show_bug.cgi?id=10994



Contributed by pablomme@googlemail.com, coenraad@wish.org.za
and a few others.

Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>