powerpc/8xx: refactor programming of microcode CPM params.

The CPM registers RCCR and CPMCR1..4 registers has to be set in
accordance with the microcode patch beeing programmed. Lets
define them as part of the patch set and refactor their
programming from that definition.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>