Standardize command usage messages with cmd_usage()

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/board/prodrive/pdnb3/pdnb3.c b/board/prodrive/pdnb3/pdnb3.c
index 3773ba1..9b87f6a 100644
--- a/board/prodrive/pdnb3/pdnb3.c
+++ b/board/prodrive/pdnb3/pdnb3.c
@@ -216,7 +216,7 @@
 	ulong addr;
 
 	if (argc < 2) {
-		printf ("Usage:\n%s\n", cmdtp->usage);
+		cmd_usage(cmdtp);
 		return 1;
 	}