[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>

net/mac80211/rx.c

@@ -1453,6 +1453,7 @@ static int prepare_for_handlers(struct ieee80211_sub_if_data *sdata,
 	case IEEE80211_IF_TYPE_MNTR:
 		/* take everything */
 		break;
+	case IEEE80211_IF_TYPE_INVALID:
 	case IEEE80211_IF_TYPE_MGMT:
 		/* should never get here */
 		WARN_ON(1);