perf tools: Do not change lib/api/fs/debugfs directly

perf tools: Do not change lib/api/fs/debugfs directly

The tracing_events_path is the variable we want to change via
--debugfs-dir option, not the debugfs_mountpoint.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Raphael Beamonte <raphael.beamonte@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1440596813-12844-4-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>