[MAC80211]: add "invalid" interface type

Since I cannot convince the lazy driver authors (hello Michael)
to stop (ab)using the MGMT interface type internally in their
drivers, this patch introduces a new _INVALID type especially
for their use and changes all affected drivers to use it.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/mac80211/ieee80211_iface.c b/net/mac80211/ieee80211_iface.c
index 08c1e18..ef618e94 100644
--- a/net/mac80211/ieee80211_iface.c
+++ b/net/mac80211/ieee80211_iface.c
@@ -243,6 +243,10 @@
 	ieee80211_if_sdata_deinit(sdata);
 
 	switch (sdata->type) {
+	case IEEE80211_IF_TYPE_INVALID:
+		/* cannot happen */
+		WARN_ON(1);
+		break;
 	case IEEE80211_IF_TYPE_MGMT:
 		/* nothing to do */
 		break;