powerpc/maple: Register CPC925 EDAC device on all boards with CPC925

Currently Maple setup code creates cpc925_edac device only on
Motorola ATCA-6101 blade. Make setup code check bridge revision
and enable EDAC on all U3H bridges.

Verified on Momentum MapleD (ppc970fx kit) board.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>