tracing: Add description of set_graph_notrace to tracing/README
tracing: Add description of set_graph_notrace to tracing/README

It was missing the description of set_graph_notrace file.  Add it.

Link: http://lkml.kernel.org/p/1402590233-22321-5-git-send-email-5c915a589b3ddf58cebf14bec41bcc143b37ac3c@kernel.org

Signed-off-by: Namhyung Kim <5c915a589b3ddf58cebf14bec41bcc143b37ac3c@kernel.org>
Signed-off-by: Steven Rostedt <43232e92d70cc7aa53504ad0397085ee47bad87f@goodmis.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs