OpenThread has lately got an option to provide a custom
crypto backend that replaces the default, based on mbedTLS
API. Implement a backend based on ARM PSA crypto API that
is better suited for applications willing to take advantage
of the ARM trust zone technology.
Add Kconfig option: OPENTHREAD_CRYPTO_PSA_ENABLE which
enables that backend.
Also, another Kconfig option:
OPENTHREAD_PLATFORM_KEY_REFERENCES_ENABLE, implied by the
former, which enables usage of key references instead of
literal keys in OpenThread. It will eventually allow
OpenThread applications to keep sensitive data such as
encryption keys in the secure storage, accessible from the
secure world only.
Signed-off-by: Damian Krolik <damian.krolik@nordicsemi.no>