iwlwifi: fix bug in tx byte count table

When setting invalid byte count in txq byte count table, read pointer
should be used instead of write pointer.
Reported-by: Guo, Chaohong <chaohong.guo@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-5000.c

@@ -781,7 +781,7 @@ void iwl5000_txq_update_byte_cnt_tbl(struct iwl_priv *priv,
 
 	scd_bc_tbl[txq_id].tfd_offset[write_ptr] = bc_ent;
 
-	if (txq->q.write_ptr < TFD_QUEUE_SIZE_BC_DUP)
+	if (write_ptr < TFD_QUEUE_SIZE_BC_DUP)
 		scd_bc_tbl[txq_id].
 			tfd_offset[TFD_QUEUE_SIZE_MAX + write_ptr] = bc_ent;
 }
@@ -803,7 +803,7 @@ void iwl5000_txq_inval_byte_cnt_tbl(struct iwl_priv *priv,
 	bc_ent = cpu_to_le16(1 | (sta_id << 12));
 	scd_bc_tbl[txq_id].tfd_offset[read_ptr] = bc_ent;
 
-	if (txq->q.write_ptr < TFD_QUEUE_SIZE_BC_DUP)
+	if (read_ptr < TFD_QUEUE_SIZE_BC_DUP)
 		scd_bc_tbl[txq_id].
 			tfd_offset[TFD_QUEUE_SIZE_MAX + read_ptr] = bc_ent;
 }