iwlwifi: mvm: use match_string() helper

match_string() returns the index of an array for a matching string,
which can be used intead of open coded variant.
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/debugfs.c

@@ -666,16 +666,11 @@ iwl_dbgfs_bt_force_ant_write(struct iwl_mvm *mvm, char *buf,
 	};
 	int ret, bt_force_ant_mode;
 
-	for (bt_force_ant_mode = 0;
-	     bt_force_ant_mode < ARRAY_SIZE(modes_str);
-	     bt_force_ant_mode++) {
-		if (!strcmp(buf, modes_str[bt_force_ant_mode]))
-			break;
-	}
-
-	if (bt_force_ant_mode >= ARRAY_SIZE(modes_str))
-		return -EINVAL;
+	ret = match_string(modes_str, ARRAY_SIZE(modes_str), buf);
+	if (ret < 0)
+		return ret;
 
+	bt_force_ant_mode = ret;
 	ret = 0;
 	mutex_lock(&mvm->mutex);
 	if (mvm->bt_force_ant_mode == bt_force_ant_mode)