Safely erase key material upon abort

Some key derivation operation contexts (like
psa_tls12_prf_key_derivation_t) directly contain buffers with parts of
the derived key. Erase them safely as part of the abort.
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index bf425df..924b291 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -3902,7 +3902,7 @@
     {
         status = PSA_ERROR_BAD_STATE;
     }
-    memset( operation, 0, sizeof( *operation ) );
+    mbedtls_platform_zeroize( operation, sizeof( *operation ) );
     return( status );
 }