Actually run MD<->PSA test, and fix it

Signed-off-by: Manuel Pégourié-Gonnard <[email protected]>

tests/suites/test_suite_md.data

@@ -2,6 +2,9 @@
 MD list
 mbedtls_md_list:
 
+MD <-> PSA conversion
+md_to_from_psa:
+
 MD NULL/uninitialised arguments
 md_null_args:
 

tests/suites/test_suite_md.function

@@ -58,7 +58,7 @@ void md_to_from_psa()
     MD_PSA(MBEDTLS_MD_SHA3_384, PSA_ALG_SHA3_384);
     MD_PSA(MBEDTLS_MD_SHA3_512, PSA_ALG_SHA3_512);
 
-    MD_PSA(MBEDTLS_MD_NONE, PSA_ALG_NONE);
+    /* Don't test for NONE<->NONE as this is not guaranteed */
 }
 /* END_CASE */