cfg80211: add feature to hold bss

In beacon filtering there needs to be a way to not expire the BSS even
when no beacons are received. Add an interface to cfg80211 to hold
BSS and make sure that it's not expired.

Signed-off-by: Kalle Valo <kalle.valo@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/wireless/core.h

@@ -90,6 +90,8 @@ struct cfg80211_internal_bss {
 	struct rb_node rbn;
 	unsigned long ts;
 	struct kref ref;
+	bool hold;
+
 	/* must be last because of priv member */
 	struct cfg80211_bss pub;
 };