cmd: efi_loader: Return CMD_RET_USAGE in case of not enough arguments

When typing 'bootefi' from U-Boot shell, nothing outputs. Like other
commands, return CMD_RET_USAGE so that it can print help message.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Alexander Graf <agraf@suse.de>

cmd/bootefi.c

@@ -226,7 +226,7 @@ static int do_bootefi(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 	int r = 0;
 
 	if (argc < 2)
-		return 1;
+		return CMD_RET_USAGE;
 	saddr = argv[1];
 
 	addr = simple_strtoul(saddr, NULL, 16);