In certain Trusted OS implementations it is a requirement to pass them the
highest power level which will enter a power down state during a PSCI
CPU_SUSPEND or SYSTEM_SUSPEND API invocation. This patch passes this power level
to the SPD in the "max_off_pwrlvl" parameter of the svc_suspend() hook.

Currently, the highest power level which was requested to be placed in a low
power state (retention or power down) is passed to the SPD svc_suspend_finish()
hook. This hook is called after emerging from the low power state. It is more
useful to pass the highest power level which was powered down instead. This
patch does this by changing the semantics of the parameter passed to an SPD's
svc_suspend_finish() hook. The name of the parameter has been changed from
"suspend_level" to "max_off_pwrlvl" as well. Same changes have been made to the
parameter passed to the tsp_cpu_resume_main() function.

NOTE: THIS PATCH CHANGES THE SEMANTICS OF THE EXISTING "svc_suspend_finish()"
      API BETWEEN THE PSCI AND SPD/SP IMPLEMENTATIONS. THE LATTER MIGHT NEED
      UPDATES TO ENSURE CORRECT BEHAVIOUR.

Change-Id: If3a9d39b13119bbb6281f508a91f78a2f46a8b90