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/amcc/taishan/lcd.c b/board/amcc/taishan/lcd.c
index 6a049df..7f7730a 100644
--- a/board/amcc/taishan/lcd.c
+++ b/board/amcc/taishan/lcd.c
@@ -166,19 +166,17 @@
 }
 static int do_lcd_puts(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);
+
 	lcd_puts(argv[1]);
 	return 0;
 }
 static int do_lcd_putc(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);
+
 	lcd_putc((char)argv[1][0]);
 	return 0;
 }
@@ -188,10 +186,8 @@
 	ulong dir;
 	char cur_addr;
 
-	if (argc < 3) {
-		cmd_usage(cmdtp);
-		return 1;
-	}
+	if (argc < 3)
+		return cmd_usage(cmdtp);
 
 	count = simple_strtoul(argv[1], NULL, 16);
 	if (count > 31) {