iwlagn: more comments for bt channel inhibition

Add comments for better description

Signed-off-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-shared.h b/drivers/net/wireless/iwlwifi/iwl-shared.h
index ec71ec7..6c20d03 100644
--- a/drivers/net/wireless/iwlwifi/iwl-shared.h
+++ b/drivers/net/wireless/iwlwifi/iwl-shared.h
@@ -91,7 +91,7 @@
 	int power_level;	/* def: 1 = power level */
 	u32 debug_level;	/* levels are IWL_DL_* */
 	int ant_coupling;
-	bool bt_ch_announce;
+	bool bt_ch_announce;	/* def: enable = BT channel inhibition */
 	int wanted_ucode_alternative;
 	bool auto_agg;		/* def: true = enable agg. without check */
 };