GitLab

- Use CMake as the build system. CMSIS build and CMSIS packs
have been removed as a consequence.
- Use Open IoT SDK instead of gitmodules to fetch dependencies.
- Use AWS embedded C SDK instead of Amazon FreeRTOS distribution
- Use MCU Driver HAL for serial, SAI and EMAC driver.
- Move TF-M target into BSP
Signed-off-by: Vincent Coubard <vincent.coubard@arm.com>