iwlagn: remove un-necessary step

No need to copy twice.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -2666,8 +2666,7 @@ lq_update:
 
 out:
 	tbl->current_rate = rate_n_flags_from_tbl(priv, tbl, index, is_green);
-	i = index;
-	lq_sta->last_txrate_idx = i;
+	lq_sta->last_txrate_idx = index;
 }
 
 /**