cmd_usage(): simplify return code handling

Lots of code use this construct:

	cmd_usage(cmdtp);
	return 1;

Change cmd_usage() let it return 1 - then we can replace all these
ocurrances by

	return cmd_usage(cmdtp);

This fixes a few places with incorrect return code handling, too.

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/board/digsy_mtc/cmd_mtc.c b/board/digsy_mtc/cmd_mtc.c
index 621980d..ba0c367 100644
--- a/board/digsy_mtc/cmd_mtc.c
+++ b/board/digsy_mtc/cmd_mtc.c
@@ -75,10 +75,8 @@
 	int err;
 	int i;
 
-	if (argc < 2) {
-		cmd_usage(cmdtp);
-		return -1;
-	}
+	if (argc < 2)
+		return cmd_usage(cmdtp);
 
 	memset(&pcmd, 0, sizeof(pcmd));
 	memset(&prx, 0, sizeof(prx));
@@ -149,10 +147,8 @@
 	int err;
 	uchar channel_mask = 0;
 
-	if (argc < 3) {
-		cmd_usage(cmdtp);
-		return -1;
-	}
+	if (argc < 3)
+		return cmd_usage(cmdtp);
 
 	if (strncmp(argv[1], "on", 2) == 0)
 		channel_mask |= 1;
@@ -178,10 +174,8 @@
 	int err;
 	uchar channel_num = 0;
 
-	if (argc < 2) {
-		cmd_usage(cmdtp);
-		return -1;
-	}
+	if (argc < 2)
+		return cmd_usage(cmdtp);
 
 	channel_num = simple_strtol(argv[1], NULL, 10);
 	if ((channel_num != 1) && (channel_num != 2)) {
@@ -332,8 +326,7 @@
 		return c->cmd(c, flag, argc, argv);
 	} else {
 		/* Unrecognized command */
-		cmd_usage(cmdtp);
-		return 1;
+		return cmd_usage(cmdtp);
 	}
 
 	return err;