ARM: hisi/hip04: remove the MCPM overhead

This platform is currently relying on the MCPM infrastructure for no
apparent reason.  The MCPM concurrency handling brings no benefits here
as there is no asynchronous CPU wake-ups to be concerned about (this is
used for CPU hotplug and secondary boot only, not for CPU idle).

This platform is also different from the other MCPM users because a given
CPU can't shut itself down completely without the assistance of another
CPU. This is at odds with the on-going MCPM backend refactoring.

To simplify things, this is converted to hook directly into the
smp_operations callbacks, bypassing the MCPM infrastructure.

Tested-by: Wei Xu <xuwei5@hisilicon.com>
Cc: Haojian Zhuang <haojian.zhuang@linaro.org>
Signed-off-by: Nicolas Pitre <nico@linaro.org>