wireless: move IEEE80211_NUM_ACS to ieee80211.h

This constant isn't really specific to mac80211, so move it
"up" a level to ieee80211.h

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/include/linux/ieee80211.h b/include/linux/ieee80211.h
index fe84932..87d1937 100644
--- a/include/linux/ieee80211.h
+++ b/include/linux/ieee80211.h
@@ -185,6 +185,8 @@
 
 /* number of user priorities 802.11 uses */
 #define IEEE80211_NUM_UPS		8
+/* number of ACs */
+#define IEEE80211_NUM_ACS		4
 
 #define IEEE80211_QOS_CTL_LEN		2
 /* 1d tag mask */