powerpc/85xx: remove P1020RDB and P2020RDB CAMP device trees

We only need two examples of CAMP device trees in the upstream kernel.

Co-operative Asymmetric Multi-Processing (CAMP) is a technique where two
or more operating systems (typically multiple copies of the same Linux
kernel) are loaded into memory, and each kernel is given a subset of the
available cores to execute on.  For example, on a four-core system, one
kernel runs on cores 0 and 1, and the other runs on cores 2 and 3.

The devices are also partitioned among the operating systems, and this is
done with customized device trees.  Each kernel gets its own device tree
that has only the devices that it should know about.

Unfortunately, this approach is very hackish.  The kernels are trusted to
only access devices in their respective device trees, and the partitioning
only works for devices that can be handled.  Crafting the device trees is a
tricky process, and getting U-Boot to load and start all kernels is
cumbersome.

But most importantly, each CAMP setup is very application-specific, since
the actual partitioning of resources is done in the DTS by the system
designer.  Therefore, it doesn't make a lot of sense to have a lot of CAMP
device trees, since we only expect them to be used as examples.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>