perf list: Avoid confusion of perf output and the next command prompt

Distinguish the output of 'perf list --list-opts' or 'perf --list-cmds'
with the next command prompt, which also happens in other cases (e.g.
record, report ...).

Example:

Before this patch:

 $perf list --list-opts
 --raw-dump $          <-- the output and the next command prompt are at
                           the same line

After this patch:

 $perf list --list-opts
 --raw-dump
 $                     <-- the new line

Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1425032491-20224-6-git-send-email-yunlong.song@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index f3c66b8..3df2665 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -223,6 +223,7 @@
 				struct cmd_struct *p = commands+i;
 				printf("%s ", p->cmd);
 			}
+			putchar('\n');
 			exit(0);
 		} else if (!strcmp(cmd, "--debug")) {
 			if (*argc < 2) {