RSA: Use hashlen as the hash input size as documented

Where hashlen was previously ignored when the hash length could be
inferred from an md_alg parameter, the two must now match.

Adapt the existing tests accordingly. Adapt the sample programs accordingly.

This commit does not add any negative testing.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

programs/pkey/dh_client.c

@@ -221,7 +221,7 @@ int main( void )
     }
 
     if( ( ret = mbedtls_rsa_pkcs1_verify( &rsa, MBEDTLS_MD_SHA256,
-                                          0, hash, p ) ) != 0 )
+                                          32, hash, p ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_rsa_pkcs1_verify returned %d\n\n", ret );
         goto exit;