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* Move libfdt API headers to include/lib/libfdt
* Add libfdt.mk helper makefile
* Remove unused libfdt files
* Minor changes to fdt.h and libfdt.h to make them C99 compliant
Co-Authored-By: Jens Wiklander <jens.wiklander@linaro.org>

Change-Id: I425842c2b111dcd5fb6908cc698064de4f77220e

Imports libfdt code from https://git.kernel.org/cgit/utils/dtc/dtc.git
tag "v1.4.1" commit 302fca9f4c283e1994cf0a5a9ce1cf43ca15e6d2.

Change-Id: Ia0d966058beee55a9047e80d8a05bbe4f71d8446