include/net/ieee80211.h must #include <linux/wireless.h>

-Wundef found an (although perhaps harmless) bug:

<-- snip -->

...
CC net/ieee80211/ieee80211_crypt.o
In file included from net/ieee80211/ieee80211_crypt.c:21:
include/net/ieee80211.h:26:5: warning: "WIRELESS_EXT" is not defined
CC net/ieee80211/ieee80211_crypt_wep.o
In file included from net/ieee80211/ieee80211_crypt_wep.c:20:
include/net/ieee80211.h:26:5: warning: "WIRELESS_EXT" is not defined
CC net/ieee80211/ieee80211_crypt_ccmp.o
CC net/ieee80211/ieee80211_crypt_tkip.o
In file included from net/ieee80211/ieee80211_crypt_tkip.c:23:
include/net/ieee80211.h:26:5: warning: "WIRELESS_EXT" is not defined
...

<-- snip -->

@@ -22,6 +22,7 @@
 #define IEEE80211_H
 #include <linux/if_ether.h> /* ETH_ALEN */
 #include <linux/kernel.h>   /* ARRAY_SIZE */
+#include <linux/wireless.h>
 
 #if WIRELESS_EXT < 17
 #define IW_QUAL_QUAL_INVALID   0x10