tracing: Add 'free' file to remove multibuffer instances Add a 'free' file that is used to remove multibuffer instances. Example: echo hello > /debug/tracing/instances/new ls /debug/tracing/instances free hello/ new echo hello > /debug/tracing/instances/free ls /debug/tracing/instances free new Signed-off-by: Steven Rostedt <rostedt@goodmis.org>