perf tools: Allow use of an exclusive option more than once

The exclusive options are to prohibit use of conflicting options at the
same time.  But it had a side effect that it also limits a such option
can be used at most once.  Currently the only user of the flag is perf
probe and it allows to use such options more than once, but when one
tries to use it, perf will fail like below:

  $ sudo perf probe -x /lib/libc-2.20.so --add malloc --add free
    Error: option `add' cannot be used with add
  ...
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1420886028-15135-1-git-send-email-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/parse-options.c

@@ -46,7 +46,7 @@ static int get_value(struct parse_opt_ctx_t *p,
 		return opterror(opt, "is not usable", flags);
 
 	if (opt->flags & PARSE_OPT_EXCLUSIVE) {
-		if (p->excl_opt) {
+		if (p->excl_opt && p->excl_opt != opt) {
 			char msg[128];
 
 			if (((flags & OPT_SHORT) && p->excl_opt->short_name) ||