libertas: misc power saving adjusts

* firmware for the CF card supports power saving
* the driver currenly only accept "iwconfig ethX power on|off", so
  I fixed what the range wext ioctl reports.
* initialize value/flags in lbs_get_power()
* get rid of unused parameter psmode in lbs_ps_confirm_sleep()
* some minor debug output tweaks

Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>