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/common/cmd_ext2.c b/common/cmd_ext2.c
index 49021cd..35fb361 100644
--- a/common/cmd_ext2.c
+++ b/common/cmd_ext2.c
@@ -65,10 +65,9 @@
 	block_dev_desc_t *dev_desc=NULL;
 	int part_length;
 
-	if (argc < 3) {
-		cmd_usage(cmdtp);
-		return 1;
-	}
+	if (argc < 3)
+		return cmd_usage(cmdtp);
+
 	dev = (int)simple_strtoul (argv[2], &ep, 16);
 	dev_desc = get_dev(argv[1],dev);
 
@@ -164,8 +163,7 @@
 		break;
 
 	default:
-		cmd_usage(cmdtp);
-		return 1;
+		return cmd_usage(cmdtp);
 	}
 
 	if (!filename) {