config: don't define CONFIG_ARCH_DEVICE_TREE

Now that nothing uses CONFIG_ARCH_DEVICE_TREE, stop defining it.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>

arch/x86/cpu/coreboot/config.mk

@@ -1,7 +0,0 @@
-#
-# Copyright (c) 2012 The Chromium OS Authors.
-#
-# SPDX-License-Identifier:	GPL-2.0+
-#
-
-CONFIG_ARCH_DEVICE_TREE := coreboot