policer:  improvement show policer cli.

cli show policer's help info is not consistent
with it's arguments.

Type: improvement

Signed-off-by: Huawei LI <lihuawei_zzu@163.com>
Change-Id: I8332fe97ba343e98511db9ff1bb6afd6f3c657cd
diff --git a/src/vnet/policer/policer.c b/src/vnet/policer/policer.c
index 0513563..9dd50b8 100644
--- a/src/vnet/policer/policer.c
+++ b/src/vnet/policer/policer.c
@@ -778,9 +778,9 @@
 
 /* *INDENT-OFF* */
 VLIB_CLI_COMMAND (show_policer_command, static) = {
-    .path = "show policer",
-    .short_help = "show policer [name]",
-    .function = show_policer_command_fn,
+  .path = "show policer",
+  .short_help = "show policer [name <name>]",
+  .function = show_policer_command_fn,
 };
 /* *INDENT-ON* */