Standardize command usage messages with cmd_usage()

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/common/cmd_date.c b/common/cmd_date.c
index b4d9649..d6bd931 100644
--- a/common/cmd_date.c
+++ b/common/cmd_date.c
@@ -89,7 +89,7 @@
 
 		break;
 	default:
-		printf ("Usage:\n%s\n", cmdtp->usage);
+		cmd_usage(cmdtp);
 		rcode = 1;
 	}