tracing: Add ftrace events for graph tracer

Add ftrace events for graph tracer, so the graph output could be shared
with other tracers.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
LKML-Reference: <1270227683-14631-2-git-send-email-jolsa@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>