mac80211: dont use interface indices in drivers

This patch gets rid of the if_id stuff where possible in favour of
a new per-virtual-interface structure "struct ieee80211_vif". This
structure is located at the end of the per-interface structure and
contains a variable length driver-use data area.

This has two advantages:
 * removes the need to look up interfaces by if_id, this is better
   for working with network namespaces and performance
 * allows drivers to store and retrieve per-interface data without
   having to allocate own lists/hash tables

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

drivers/net/wireless/ath5k/base.h

@@ -123,7 +123,7 @@ struct ath5k_softc {
 	unsigned int		curmode;	/* current phy mode */
 	struct ieee80211_channel *curchan;	/* current h/w channel */
 
-	int 			iface_id;	/* add/remove_interface id */
+	struct ieee80211_vif *vif;
 
 	struct {
 		u8	rxflags;	/* radiotap rx flags */