Bluetooth: Add support for sending system notes to monitor channel

The monitor channel can be used to send generic system notes as text
strings for debugging purposes. This adds the system note monitor code
and uses it for including kernel and subsystem version into traces.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
index 8d38f41..bfd1590 100644
--- a/include/net/bluetooth/bluetooth.h
+++ b/include/net/bluetooth/bluetooth.h
@@ -29,6 +29,8 @@
 #include <net/sock.h>
 #include <linux/seq_file.h>
 
+#define BT_SUBSYS_VERSION "2.21"
+
 #ifndef AF_BLUETOOTH
 #define AF_BLUETOOTH	31
 #define PF_BLUETOOTH	AF_BLUETOOTH