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/freescale/common/sys_eeprom.c b/board/freescale/common/sys_eeprom.c
index 5a8f4f5..3929ad0 100644
--- a/board/freescale/common/sys_eeprom.c
+++ b/board/freescale/common/sys_eeprom.c
@@ -351,8 +351,7 @@
 			prog_eeprom();
 			break;
 		default:
-			cmd_usage(cmdtp);
-			break;
+			return cmd_usage(cmdtp);
 		}
 
 		return 0;
@@ -388,8 +387,7 @@
 		break;
 	case 'h':	/* help */
 	default:
-		cmd_usage(cmdtp);
-		break;
+		return cmd_usage(cmdtp);
 	}
 
 	return 0;