perf top: Fix code typo in prompt_symbol()

sym_filter is what was (if ever) passed with -s option. What was
typed by user, and what we were looking for, is in buf.

Signed-off-by: Kirill Smelkov <kirr@landau.phys.spbu.ru>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <1263396139-4798-3-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/builtin-top.c

@@ -667,7 +667,7 @@ static void prompt_symbol(struct sym_entry **target, const char *msg)
 	}
 
 	if (!found) {
-		fprintf(stderr, "Sorry, %s is not active.\n", sym_filter);
+		fprintf(stderr, "Sorry, %s is not active.\n", buf);
 		sleep(1);
 		return;
 	} else