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/arch/powerpc/cpu/mpc83xx/ecc.c b/arch/powerpc/cpu/mpc83xx/ecc.c
index 8dadd64..f8eab96 100644
--- a/arch/powerpc/cpu/mpc83xx/ecc.c
+++ b/arch/powerpc/cpu/mpc83xx/ecc.c
@@ -118,10 +118,8 @@
 	writeback[0] = 0x01234567UL;
 	writeback[1] = 0x89abcdefUL;
 
-	if (argc > 4) {
-		cmd_usage(cmdtp);
-		return 1;
-	}
+	if (argc > 4)
+		return cmd_usage(cmdtp);
 
 	if (argc == 2) {
 		if (strcmp(argv[1], "status") == 0) {
@@ -350,8 +348,7 @@
 			return 0;
 		}
 	}
-	cmd_usage(cmdtp);
-	return 1;
+	return cmd_usage(cmdtp);
 }
 
 U_BOOT_CMD(ecc, 4, 0, do_ecc,