iwlwifi: scan correct setting of valid rx_chains

This patch sets rx_chain bitmap correctly according hw configuration.
Signed-off-by: NTomas Winkler <tomas.winkler@intel.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

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

@@ -703,7 +703,7 @@ static void iwl_bg_request_scan(struct work_struct *data)
 	u16 cmd_len;
 	enum ieee80211_band band;
 	u8 n_probes = 2;
-	u8 rx_chain = 0x7; /* bitmap: ABC chains */
+	u8 rx_chain = priv->hw_params.valid_rx_ant;
 
 	conf = ieee80211_get_hw_conf(priv->hw);