powerpc: broadway processor support

This patch extends the cputable entry of the 750CL to also match
the 750CL-based "Broadway" cpu found on the Nintendo Wii.

As of this patch, the following "Broadway" design revision levels have
been seen in the wild:
- DD1.2 (87102)
- DD2.0 (87200)

Signed-off-by: Albert Herranz <albert_herranz@yahoo.es>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>