tools lib api fs: Add {tracefs,debugfs}_configured() functions

Add tracefs_configured() to return true if tracefs is configured in the
kernel (succeeds to find tracefs), and debugfs_configured() if debugfs
is configured in the kernel (succeeds to find debugfs).

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20150202193553.190606690@goodmis.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>