iwlwifi: fix clear statistics counter command

When receive reply statistics command with "clear" mask, just reset the
accumulated statistics counters, but not the current statistics counters,
so the accumulated statistics counter can provide the correct
information.

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-rx.c

@@ -638,8 +638,6 @@ void iwl_reply_statistics(struct iwl_priv *priv,
 	struct iwl_rx_packet *pkt = rxb_addr(rxb);
 
 	if (le32_to_cpu(pkt->u.stats.flag) & UCODE_STATISTICS_CLEAR_MSK) {
-		memset(&priv->statistics, 0,
-			sizeof(struct iwl_notif_statistics));
 #ifdef CONFIG_IWLWIFI_DEBUG
 		memset(&priv->accum_statistics, 0,
 			sizeof(struct iwl_notif_statistics));