cpuidle: governors: Remove remaining old module code

The governor's code use try_module_get() and put_module() to refcount
the governor's module. But the governors are not compiled as module.

The refcount does not prevent to switch the governor or unload
a module as they aren't compiled as modules. The code is pointless,
so remove it.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>