iwlwifi: optimize power saving

In hostap AP mode, every time the client sends the AP
a packet the STA_NOTIFY_AWAKE code is sent from mac80211.
This results in a command being sent to the uCode even if
the client was not asleep.

The following simple patch has fixed the issue for me without any
degradation that I can find.

Signed-off-by: Daniel Halperin <dhalperi@cs.washington.edu>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>