perf probe: Fix build error of builtin-probe.c

I got this build error when building tip tree:

| cc1: warnings being treated as errors
| builtin-probe.c:123: error: 'opt_show_lines' defined but not used

This error is caused by:

| #ifndef NO_LIBDWARF
|	OPT_CALLBACK('L', "line", NULL,
|		     "FUNC[:RLN[+NUM|:RLN2]]|SRC:ALN[+NUM|:ALN2]",
|		     "Show source code lines.", opt_show_lines),
| #endif

My environment defines NO_LIBDWARF, so gcc treated
opt_show_lines() as garbage. So I moved opt_show_lines() into
#ifndef NO_LIBDWARF ... #endif block.
Signed-off-by: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <1263645076-9993-1-git-send-email-mitake@dcl.info.waseda.ac.jp>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/builtin-probe.c

@@ -118,15 +118,6 @@ static int opt_del_probe_event(const struct option *opt __used,
 	return 0;
 }
 
-static int opt_show_lines(const struct option *opt __used,
-			  const char *str, int unset __used)
-{
-	if (str)
-		parse_line_range_desc(str, &session.line_range);
-	INIT_LIST_HEAD(&session.line_range.line_list);
-	session.show_lines = true;
-	return 0;
-}
 /* Currently just checking function name from symbol map */
 static void evaluate_probe_point(struct probe_point *pp)
 {
@@ -148,6 +139,16 @@ static int open_vmlinux(void)
 	pr_debug("Try to open %s\n", session.kmap->dso->long_name);
 	return open(session.kmap->dso->long_name, O_RDONLY);
 }
+
+static int opt_show_lines(const struct option *opt __used,
+			  const char *str, int unset __used)
+{
+	if (str)
+		parse_line_range_desc(str, &session.line_range);
+	INIT_LIST_HEAD(&session.line_range.line_list);
+	session.show_lines = true;
+	return 0;
+}
 #endif
 
 static const char * const probe_usage[] = {