Improve and fix various things in the MPC8xx FEC driver:
1. The new 87x and 88x series of processors have two FECs,
   and the new driver supports them both.
2. Another change in the 87x/88x series is support for
   the RMII (Reduced MII) interface. However numerous
   changes are needed to make it work since the PHYs
   are connected to the same lines. That means that
   you have to address them correctly over the MII
   interface.