This commit allows for Zephyr modules to be natively integrated into
the build system with CMakeLists.txt and Kconfig files.
The sourcing of module files are done in following order:
- If <module>/zephyr/module.yml exists, use cmake and kconfig settings
for sourcing of additional file
- Else if <module>/zephyr/CMakeLists.txt exists, source this file into
CMake build tree and add <module>/zephyr/Kconfig as osource
If none of the above files are present, the project is considered to
not be a Zephyr module
Signed-off-by: Torsten Rasmussen <torsten.rasmussen@nordicsemi.no>