lib: utils: Add a fdt_reserved_memory_fixup() helper

Add a helper routine to insert a child node of the reserved memory
node in the device tree that describes the protected memory region
done by OpenSBI via PMP.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>

lib/utils/fdt/objects.mk

@@ -0,0 +1,7 @@
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (C) 2020 Bin Meng <bmeng.cn@gmail.com>
+#
+
+libsbiutils-objs-y += fdt/fdt_helper.o