mac80211: integrate sta_notify_ps cmds into sta_notify

This patch replaces the newly introduced sta_notify_ps function,
which can be used to notify the driver about every power state
transition for all associated stations, by integrating its functionality
back into the original sta_notify callback.

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