MD2 and MD4 were declared as enabled (PSA_WANT_ALG_MD{2,4} defined) but not
actually implemented in the test driver (MBEDTLS_MD{2,4}_C) not defined. Fix
this inconsistency caued deterministic ECDSA tests using those hashes to
fail. Now MD2 and MD4 are consistently off and the offending test cases
don't run.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>