cpc925_edac: convert driver to use the new edac ABI

The legacy edac ABI is going to be removed. Port the driver to use
and benefit from the new API functionality.

Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michal Marek <mmarek@suse.cz>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>