The pk_rsa_encrypt_test_vec() reference vector is calculated while using
mbedtls_test_rnd_pseudo_rand rng source, but since the RNG souce can't
be controlled when USE_PSA_CRYPTO is enabled we can't get the same
result.
The pk_rsa_encrypt_test_vec() fails when switching to mbedtls_test_rnd_std_rand
as rng source.
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>