Standardize command usage messages with cmd_usage()

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/board/lwmon/lwmon.c b/board/lwmon/lwmon.c
index 878752c..257f1cd 100644
--- a/board/lwmon/lwmon.c
+++ b/board/lwmon/lwmon.c
@@ -846,7 +846,7 @@
 	default:
 		break;
 	}
-	printf ("Usage:\n%s\n", cmdtp->usage);
+	cmd_usage(cmdtp);
 	return 1;
 }
 U_BOOT_CMD(
@@ -976,7 +976,7 @@
 	default:
 		break;
 	}
-	printf ("Usage:\n%s\n", cmdtp->usage);
+	cmd_usage(cmdtp);
 	return 1;
 }