perf probe: Warn when more than one line are given

Check multiple --lines option and print warning informing that only the
first specified --line option is valid.

Changes from the 1st post:

- Accept only the first option instead of the last.
- Fix warning message according to David's comment.
- Mark as a bugfix.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: yrl.pp-manager.tt@hitachi.com
Link: http://lkml.kernel.org/r/20110811110253.19900.96192.stgit@fedora15Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-probe.c

@@ -134,10 +134,18 @@ static int opt_show_lines(const struct option *opt __used,
 {
 	int ret = 0;
 
-	if (str)
+	if (!str)
+		return 0;
+
+	if (params.show_lines) {
+		pr_warning("Warning: more than one --line options are"
+			   " detected. Only the first one is valid.\n");
+		return 0;
+	}
+
+	params.show_lines = true;
 	ret = parse_line_range_desc(str, &params.line_range);
 	INIT_LIST_HEAD(&params.line_range.line_list);
-	params.show_lines = true;
 
 	return ret;
 }