ENGR00209520-03 - FEC : Add support for MX6SL MSL.

ENGR00209520-03 - FEC : Add support for MX6SL MSL.

- Modify the the platform macro define like as cpu_is_xxx()
  for supporting Mergrez chip.
- Config MIIGSK for FEC IP to enable RMII mode. MX25,MX53,
  and MX6Sololite use FEC IP, which need to config the MIIGSK
  registers memory map for RMII and MII.
- Correct device id_table entry name for differnt IP.
- Rewrite FEC MAC address by net_device address when reset FEC,
  which can avoid invalid MAC address to result in FEC cannot
  work.

Signed-off-by: Fugang Duan <B38611@freescale.com>