iwlagn: add bluetooth stats to debugfs

For WiFi/BT combo devices, add bluetooth statistics counter
read function to debugfs.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-agn-debugfs.h b/drivers/net/wireless/iwlwifi/iwl-agn-debugfs.h
index 59b1f25..bbdce59 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn-debugfs.h
+++ b/drivers/net/wireless/iwlwifi/iwl-agn-debugfs.h
@@ -37,6 +37,8 @@
 				size_t count, loff_t *ppos);
 ssize_t iwl_ucode_general_stats_read(struct file *file, char __user *user_buf,
 				     size_t count, loff_t *ppos);
+ssize_t iwl_ucode_bt_stats_read(struct file *file, char __user *user_buf,
+				size_t count, loff_t *ppos);
 #else
 static ssize_t iwl_ucode_rx_stats_read(struct file *file, char __user *user_buf,
 				       size_t count, loff_t *ppos)
@@ -53,4 +55,9 @@
 {
 	return 0;
 }
+static ssize_t iwl_ucode_bt_stats_read(struct file *file, char __user *user_buf,
+				       size_t count, loff_t *ppos)
+{
+	return 0;
+}
 #endif