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>
diff --git a/drivers/net/wireless/rtl8180.h b/drivers/net/wireless/rtl8180.h
index 0b333ca..2cbfe3c 100644
--- a/drivers/net/wireless/rtl8180.h
+++ b/drivers/net/wireless/rtl8180.h
@@ -90,8 +90,8 @@
 	/* common between rtl818x drivers */
 	struct rtl818x_csr __iomem *map;
 	const struct rtl818x_rf_ops *rf;
+	struct ieee80211_vif *vif;
 	int mode;
-	int if_id;
 
 	/* rtl8180 driver specific */
 	spinlock_t lock;