iwlwifi: only update byte count table during aggregation

The byte count table is only used for aggregation. Updating it
in other cases caused fragmented frames to be dropped.

This fixes http://www.intellinuxwireless.org/bugzilla/show_bug.cgi?id=2004

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-tx.c

@@ -872,7 +872,8 @@ int iwl_tx_skb(struct iwl_priv *priv, struct sk_buff *skb)
 	iwl_print_hex_dump(priv, IWL_DL_TX, (u8 *)tx_cmd->hdr, hdr_len);
 
 	/* Set up entry for this TFD in Tx byte-count array */
-	priv->cfg->ops->lib->txq_update_byte_cnt_tbl(priv, txq,
+	if (info->flags & IEEE80211_TX_CTL_AMPDU)
+		priv->cfg->ops->lib->txq_update_byte_cnt_tbl(priv, txq,
 						     le16_to_cpu(tx_cmd->len));
 
 	pci_dma_sync_single_for_device(priv->pci_dev, txcmd_phys,