Standardize command usage messages with cmd_usage()

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/common/cmd_net.c b/common/cmd_net.c
index c053d7b..b627c38 100644
--- a/common/cmd_net.c
+++ b/common/cmd_net.c
@@ -186,7 +186,7 @@
 
 		break;
 
-	default: printf ("Usage:\n%s\n", cmdtp->usage);
+	default: cmd_usage(cmdtp);
 		show_boot_progress (-80);
 		return 1;
 	}
@@ -251,7 +251,7 @@
 
 	NetPingIP = string_to_ip(argv[1]);
 	if (NetPingIP == 0) {
-		printf ("Usage:\n%s\n", cmdtp->usage);
+		cmd_usage(cmdtp);
 		return -1;
 	}