mac80211: only transition STAs ps->wake on data frames

When a station goes to PS mode to scan, it will then send
probe requests without the PS bit set. mac80211 will take
that as indication that the station woke up, but it didn't.
This patch changes mac80211 to only consider doze->wake
transitions on data frames to to fix that issue.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Jouni Malinen <j@w1.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>