[POWERPC] 4xx: Add 405GPr and 405EP support in boot wrapper

This patch adds support for 405GPr processors with optional
new mode strapping. ibm405gp_fixup_clocks() can now be used
for 405GP and 405GPr CPUs.

This is in preparation of porting the cpci405 platform support
from arch/ppc to arch/powerpc.

This patch also adds ibm405ep_fixup_clocks() to support
405EP CPUs from the boot wrapper.

Signed-off-by: Matthias Fuchs <matthias.fuchs@esd-electronics.com>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>