mpc85xx: Add support for the Varisys Cyrus board

This board runs a P5020 or P5040 chip, and utilizes
an EEPROM with similar formatting to the Freescale P5020DS.

Large amounts of this code were developed by
Adrian Cox <adrian at humboldt dot co dot uk>

Signed-off-by: Andy Fleming <afleming@gmail.com>
Reviewed-by: York Sun <yorksun@freescale.com>