mac80211: disable uAPSD if all ACs are under ACM

It's unlikely that an AP requires WMM mandatory admission control
for all access categories, and if it does then we still transmit
on the background AC without requesting admission. However, avoid
using uAPSD in this case since the implementation could run into
issues and might use other ACs etc.

Signed-off-by: Alexander Bondar <alexander.bondar@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mlme.c

@@ -4086,7 +4086,8 @@ int ieee80211_mgd_assoc(struct ieee80211_sub_if_data *sdata,
 	rcu_read_unlock();
 
 	if (bss->wmm_used && bss->uapsd_supported &&
-	    (sdata->local->hw.flags & IEEE80211_HW_SUPPORTS_UAPSD)) {
+	    (sdata->local->hw.flags & IEEE80211_HW_SUPPORTS_UAPSD) &&
+	    sdata->wmm_acm != 0xff) {
 		assoc_data->uapsd = true;
 		ifmgd->flags |= IEEE80211_STA_UAPSD_ENABLED;
 	} else {