ARM: MCPM: remove residency argument from mcpm_cpu_suspend()

This is currently unused.

If a suspend must be limited to CPU level only by preventing the last man
from triggering a cluster level suspend then this should be determined
according to many other criteria the MCPM layer is currently not aware of.
It is unlikely that mcpm_cpu_suspend() would be the proper conduit for
that information anyway.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Dave Martin <Dave.Martin@arm.com>