tools lib api fs: Make tracing_path_strerror_open message generic

Making tracing_path__strerror_open_tp message generic by mentioning both
debugfs/tracefs words in error message plus the tracing_path instead of
debugfs_mountpoint.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
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>
Cc: Raphael Beamonte <raphael.beamonte@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1441180605-24737-7-git-send-email-jolsa@kernel.org


[ Add comment for the ENOENT case out of this patch discussion thread ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>