Implement the phy-mode property for ate and macb. If it is set to

Implement the phy-mode property for ate and macb. If it is set to
"rmii", use rmii mode for the MAC, otherwise use MII mode. The code is
somewhat duplicated between these drivers for this.

Also, add AT91RM9200 compatibility strings to the ate driver. In the
future, there's a good chance that ate will lose the MACB support and
only attach to the AT91RM9200 EMAC device since the macb works now
that RMII support has been added to it.