This function, and mbedtls_psa_crypto_free, are not thread safe as they wipe slots
regardless of state. They are not part of the PSA Crypto API, untrusted applications
cannot call these functions in a crypto service.
In a service intergration, mbedtls_psa_crypto_free on the client cuts the communication
with the crypto service.
Signed-off-by: Ryan Everett <ryan.everett@arm.com>