Moving debugfs__strerror_open out of api/fs/debugfs.c, because it's not
debugfs specific. It'll be changed to consider tracefs mount as well in
following patches.

Renaming it into tracing_path__strerror_open_tp to fit into the
namespace. No functional change is intended.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Reviewed-by: Matt Fleming <matt.fleming@intel.com>
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>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1441180605-24737-6-git-send-email-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>