Fix test dependency

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>

tests/suites/test_suite_md.function

@@ -30,10 +30,12 @@ void mbedtls_md_list()
         TEST_EQUAL(0, mbedtls_md_finish(&ctx, out));
         mbedtls_md_free(&ctx);
 
+#if defined MBEDTLS_PSA_CRYPTO_C
         /* Ensure that we can convert to and from a psa_algorithm_t */
         psa_algorithm_t p = mbedtls_md_psa_alg_from_type(*md_type_ptr);
         TEST_ASSERT(p != PSA_ALG_NONE);
         TEST_EQUAL(*md_type_ptr, mbedtls_md_type_from_psa_alg(p));
+#endif
     }
 
 exit: