e500mc does not support the HID0/MSR mechanism that is used by e500_idle
(and there are also issues with waking on certain types of interrupts).

Further, even if napping is never actually enabled, just having
CPU_FTR_CAN_NAP will cause machine_init() to overwrite the board's supplied
ppc_md.power_save().

We drop CPU_FTR_MAYBE_CAN_DOZE becuase we should use 'wait' instead on
e500mc.
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>