Introduce overlay_tool.h that defines core configuration blocks from
data available in the linux architecture variant overlay.
Overlay data is automatically generated in the core configuration
process by Tensilica tools and can be directly converted to qemu xtensa
core description by overlay_tool.h
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>