The --funcs option should be given exclusively.  This adds
PARSE_OPT_EXCUSIVE flag on --funcs (-F) option.

Without this, 'perf probe --funcs -l' just shows the list of probes.

With this, it shows error message correctly.

This also fixes the help message and the documentation.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20150423134612.26128.58189.stgit@localhost.localdomainSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>