[Bluetooth] Keep rfcomm_dev on the list until it is freed

This patch changes the RFCOMM TTY release process so that the TTY is kept
on the list until it is really freed. A new device flag is used to keep
track of released TTYs.

Signed-off-by: Ville Tervo <ville.tervo@nokia.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/include/net/bluetooth/rfcomm.h b/include/net/bluetooth/rfcomm.h
index 3c563f0..25aa575 100644
--- a/include/net/bluetooth/rfcomm.h
+++ b/include/net/bluetooth/rfcomm.h
@@ -323,6 +323,7 @@
 #define RFCOMM_RELEASE_ONHUP  1
 #define RFCOMM_HANGUP_NOW     2
 #define RFCOMM_TTY_ATTACHED   3
+#define RFCOMM_TTY_RELEASED   4
 
 struct rfcomm_dev_req {
 	s16      dev_id;