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/renesas/sh7785lcr/rtl8169_mac.c b/board/renesas/sh7785lcr/rtl8169_mac.c
index dae01ec..e15013f 100644
--- a/board/renesas/sh7785lcr/rtl8169_mac.c
+++ b/board/renesas/sh7785lcr/rtl8169_mac.c
@@ -304,10 +304,8 @@
 	unsigned char mac[6];
 	char *s, *e;
 
-	if (argc != 2) {
-		cmd_usage(cmdtp);
-		return 1;
-	}
+	if (argc != 2)
+		return cmd_usage(cmdtp);
 
 	s = argv[1];
 
@@ -330,10 +328,8 @@
 
 int do_print_mac(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
-	if (argc != 1) {
-		cmd_usage(cmdtp);
-		return 1;
-	}
+	if (argc != 1)
+		return cmd_usage(cmdtp);
 
 	mac_read();