linux-phytec-ti

scripts/dtc: Bring in upstream version of fdtoverlay tool

Bring in upstream version v1.4.5.6-gc1e55a5513e9 of the fdtoverlay tool.
Copied over the fdtoverlay.c source as such, and updated the Makefile
to build the tool.

Signed-off-by: Tero Kristo <t-kristo@ti.com>