iwlwifi: take a fresh set of supported rates at each cycle

This patch fixes regression in iwlwifi IBSS rate scaling caused by the
patch named "mac80211: eliminate IBSS warning in rate_lowest_index()"
by Vladimir Koutny <vlado@work.ksp.sk>.
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn-rs.c

@@ -1668,6 +1668,7 @@ static void rs_rate_scale_perform(struct iwl_priv *priv,
 		return;
 
 	lq_sta = (struct iwl_lq_sta *)sta->rate_ctrl_priv;
+	lq_sta->supp_rates = sta->supp_rates[lq_sta->band];
 
 	tid = rs_tl_add_packet(lq_sta, hdr);