powerpc/85xx: Add support for Varisys Cyrus board

This board uses a P5020 chip, and boots just fine using
the corenet_generic code. The device tree is very similar to the
P5020DS, except that there is no Flash memory. The environment is,
instead, stored on an MMC card on the motherboard.

Signed-off-by: Andy Fleming <afleming@gmail.com>
[scottwood: fixed trailing whitespace]
Signed-off-by: Scott Wood <scottwood@freescale.com>