iwlwifi: introduce iwl_bt_statistics

We use priv->cfg->bt_params && priv->cfg->bt_params->bt_statistics
conditional in few places, merge it into one function.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-agn.c b/drivers/net/wireless/iwlwifi/iwl-agn.c
index eb16647..646ccb2 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn.c
@@ -3077,8 +3077,7 @@
 	}
 
 	if (priv->start_calib) {
-		if (priv->cfg->bt_params &&
-		    priv->cfg->bt_params->bt_statistics) {
+		if (iwl_bt_statistics(priv)) {
 			iwl_chain_noise_calibration(priv,
 					(void *)&priv->_agn.statistics_bt);
 			iwl_sensitivity_calibration(priv,