Standardize command usage messages with cmd_usage()

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/common/cmd_ubi.c b/common/cmd_ubi.c
index 5c31f7b..305e2e1 100644
--- a/common/cmd_ubi.c
+++ b/common/cmd_ubi.c
@@ -441,7 +441,7 @@
 	int err = 0;
 
 	if (argc < 2) {
-		printf("Usage:\n%s\n", cmdtp->usage);
+		cmd_usage(cmdtp);
 		return 1;
 	}
 
@@ -459,7 +459,7 @@
 		}
 
 		if (argc < 4) {
-			printf("Usage:\n%s\n", cmdtp->usage);
+			cmd_usage(cmdtp);
 			return 1;
 		}