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/lwmon5/lwmon5.c b/board/lwmon5/lwmon5.c
index 3948c13..ec113e7 100644
--- a/board/lwmon5/lwmon5.c
+++ b/board/lwmon5/lwmon5.c
@@ -306,20 +306,15 @@
 
 int do_eeprom_wp(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
-	if (argc < 2) {
-		cmd_usage(cmdtp);
-		return 1;
-	}
+	if (argc < 2)
+		return cmd_usage(cmdtp);
 
-	if ((strcmp(argv[1], "on") == 0)) {
+	if ((strcmp(argv[1], "on") == 0))
 		gpio_write_bit(CONFIG_SYS_GPIO_EEPROM_EXT_WP, 1);
-	} else if ((strcmp(argv[1], "off") == 0)) {
+	else if ((strcmp(argv[1], "off") == 0))
 		gpio_write_bit(CONFIG_SYS_GPIO_EEPROM_EXT_WP, 0);
-	} else {
-		cmd_usage(cmdtp);
-		return 1;
-	}
-
+	else
+		return cmd_usage(cmdtp);
 
 	return 0;
 }