Timing issues in microcode for some devices can cause a compressed BA to
be sent to the driver prior to returning any a-MPDU notification.
Traces show RTS-CTS is exchanged and then the timer fires which causes an
empty BA to be sent which acknowledges nothing.  This results in a noisy
printk. Only print the message if the bitmap is non-zero.
Signed-off-by:  Don Fry <donald.h.fry@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
        struct ieee80211_tx_info *info;
 
        if (unlikely(!agg->wait_for_ba))  {
-               IWL_ERR(priv, "Received BA when not expected\n");
+               if (unlikely(ba_resp->bitmap))
+                       IWL_ERR(priv, "Received BA when not expected\n");
                return -EINVAL;
        }