powercap: constify powercap_zone_ops and powercap_zone_constraint_ops structures

The powercap_zone_ops and powercap_zone_constraint_ops structures are never
modified, so declare them as const.

Most of the actual changes adjust indentation to accomodate the const
keyword.

Done with the help of Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>