p54: deactivate broken powersave function

This patch deactivates powersave in station mode.

It does not work correctly yet, so the code does more harm than good.

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>