mac80211: Enhancements to dynamic power save.

This patch enables mac80211 to send a null frame and also to
check for tim in the beacon if dynamic power save is enabled.

Signed-off-by: Vivek Natarajan <vnatarajan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index f5c7c33..a2caeed 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -395,7 +395,7 @@
 	return RX_QUEUED;
 }
 
-static void ieee80211_send_nullfunc(struct ieee80211_local *local,
+void ieee80211_send_nullfunc(struct ieee80211_local *local,
 				    struct ieee80211_sub_if_data *sdata,
 				    int powersave)
 {