ideapad_laptop: convert internal function calls to use ideapad_private as parameter

As struct ideapad_private has all the information needed for any operations,
convert ideapad_register_rfkill()/ideapad_unregister_rfkill() and
ideapad_sync_touchpad_state() to use struct ideapad_private as the parameter,
to be consistent with the others.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
CC: Matthew Garrett <matthew.garrett@nebula.com>
CC: Ike Panhc <ike.pan@canonical.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>