Bluetooth: Convert inquiry cache to use debugfs instead of sysfs

The output of the inquiry cache is only useful for debugging purposes
and so move it into debugfs.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

include/net/bluetooth/hci_core.h

@@ -134,6 +134,8 @@ struct hci_dev {
 
 	atomic_t 		promisc;
 
+	struct dentry		*debugfs;
+
 	struct device		*parent;
 	struct device		dev;