In the TLS-Exporter for TLS 1.3 we mistakenly call PSA_HASH_LENGTH() on
an mbedtls_md_type_t when it should be called on a psa_algorithm_t.
Fortunately, these two types have almost the same values, since we have
previously aligned them to make conversion more efficient. As a result,
PSA_HASH_LENGTH() produces exactly the same value when called on an
mbedtls_md_type_t as with the equivalent psa_algorithm_t.
Thanks to this happy coincidence, fix a largely cosmetic issue (rather
than a major functional bug).
Signed-off-by: David Horstmann <david.horstmann@arm.com>