Move software configuration from Zephyr samples directory
to SOF platforms directory using Zephyr overlay mechanism.
How it works:
1. Gets zephyr board defconfig values
2. Applies Zephyr samples prj.conf values on top of it
3. Then applies our new overlay.conf on top of it
4. Final "summary" of Kconfig settings is written to autoconf.h header
Signed-off-by: Andrey Borisovich <andrey.borisovich@intel.com>