ACPI / processor: remove unused variabled from acpi_processor_power structure

Few elements in the acpi_processor_power structure are unused. It could
be remnant in the header missed while the code got removed from the
corresponding driver file.

This patch removes those unused variables in the structure declaration.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>