Add boilerplate for dispatching MAC operations

Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
diff --git a/include/psa/crypto_driver_contexts_composites.h b/include/psa/crypto_driver_contexts_composites.h
index 1c71c52..239fdcb 100644
--- a/include/psa/crypto_driver_contexts_composites.h
+++ b/include/psa/crypto_driver_contexts_composites.h
@@ -49,5 +49,14 @@
  * are formatted as `'drivername'_ctx`. This allows for procedural generation
  * of both this file and the content of psa_crypto_driver_wrappers.c */
 
+typedef union {
+    unsigned dummy; /* Make sure this union is always non-empty */
+    mbedtls_psa_mac_operation_t mbedtls_ctx;
+#if defined(PSA_CRYPTO_DRIVER_TEST)
+    mbedtls_transparent_test_driver_mac_operation_t transparent_test_driver_ctx;
+    mbedtls_opaque_test_driver_mac_operation_t opaque_test_driver_ctx;
+#endif
+} psa_driver_mac_context_t;
+
 #endif /* PSA_CRYPTO_DRIVER_CONTEXTS_COMPOSITES_H */
 /* End of automatically generated file. */