mac80211: Retry probe request few times

Retry 5 times  (chosen arbitary ), before assuming
that station is out of range.

Fixes frequent disassociations while connected to weak,
and sometimes even strong access points.

Signed-off-by: Maxim Levitky <maximlevitsky@gmail.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/ieee80211_i.h

@@ -280,6 +280,7 @@ struct ieee80211_if_managed {
 	struct work_struct beacon_loss_work;
 
 	unsigned long probe_timeout;
+	int probe_send_count;
 
 	struct mutex mtx;
 	struct ieee80211_bss *associated;