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