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_cache.c b/common/cmd_cache.c
index be87b5c..5cdd834 100644
--- a/common/cmd_cache.c
+++ b/common/cmd_cache.c
@@ -34,10 +34,6 @@
 	switch (argc) {
 	case 2:			/* on / off	*/
 		switch (on_off(argv[1])) {
-#if 0	/* prevented by varargs handling; FALLTROUGH is harmless, too */
-		default: cmd_usage(cmdtp);
-			return;
-#endif
 		case 0:	icache_disable();
 			break;
 		case 1:	icache_enable ();
@@ -49,8 +45,7 @@
 			icache_status() ? "ON" : "OFF");
 		return 0;
 	default:
-		cmd_usage(cmdtp);
-		return 1;
+		return cmd_usage(cmdtp);
 	}
 	return 0;
 }
@@ -60,10 +55,6 @@
 	switch (argc) {
 	case 2:			/* on / off	*/
 		switch (on_off(argv[1])) {
-#if 0	/* prevented by varargs handling; FALLTROUGH is harmless, too */
-		default: cmd_usage(cmdtp);
-			return;
-#endif
 		case 0:	dcache_disable();
 			break;
 		case 1:	dcache_enable ();
@@ -75,8 +66,7 @@
 			dcache_status() ? "ON" : "OFF");
 		return 0;
 	default:
-		cmd_usage(cmdtp);
-		return 1;
+		return cmd_usage(cmdtp);
 	}
 	return 0;