Make sure MBEDTLS_PSA_CRYPTO_CLIENT is defined
when MBEDTLS_PSA_CRYPTO_C is defined and guard
PSA client code only with MBEDTLS_PSA_CRYPTO_CLIENT.
The definition of MBEDTLS_PSA_CRYPTO_CLIENT is done
in crypto_types.h before the definition of
psa_key_attributes_t. That way as PSA crypto client
code is related to key attributes we can be quite
confident that MBEDTLS_PSA_CRYPTO_CLIENT will be
defined when needed.
Signed-off-by: Ronald Cron <ronald.cron@arm.com>