modules: mbedtls: move CMakeLists.txt. into the main tree

We move the Zephyr-specific CMakeLists.txt file into
the main Zephyr tree. We also move the zephyr_init.c
source file.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
5 files changed