tg3: Push phylib definitions to phylib

This patch pushes phylib definitions out to phylib headers.  For phy
IDs, this removes some code duplication.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>