powerpc/8xx: move CPM1 related files from sysdev/ to platforms/8xx

Only 8xx selects CPM1 and related CONFIG options are already
in platforms/8xx/Kconfig

Move the related C files to platforms/8xx/.

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