mac80211: remove tx_frags driver callback

The implementation of tx_frags is buggy due to
not handling queue stop, and there's no driver
implementing it so remove it.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 4990f4f..364a1e7 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1295,11 +1295,8 @@
 		break;
 	}
 
-	if (local->ops->tx_frags)
-		drv_tx_frags(local, vif, pubsta, skbs);
-	else
-		result = ieee80211_tx_frags(local, vif, pubsta, skbs,
-					    txpending);
+	result = ieee80211_tx_frags(local, vif, pubsta, skbs,
+				    txpending);
 
 	ieee80211_tpt_led_trig_tx(local, fc, led_len);
 	ieee80211_led_tx(local, 1);