hw/net: create common collection of MII definitions

hw/net: create common collection of MII definitions

Create a common set of definitions of address and register values for
ethernet MII phys. A few of the current ethernet drivers have at least
a partial set of these definitions. Others just use hard coded raw
constant numbers.

This initial set is copied directly from the allwinner_emac code.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1435296436-12152-2-git-send-email-gerg@uclinux.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>