perf tools: Add tracing_path and remove unneeded functions

There's no need for find_tracing_dir, because perf already searches for
debugfs/tracefs mount on start and populate tracing_events_path.

Adding tracing_path to carry tracing dir string to be used in
get_tracing_file instead of calling find_tracing_dir.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Raphael Beamonte <raphael.beamonte@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1440596813-12844-3-git-send-email-jolsa@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>