Add static internal MAC finish function

add new psa_mac_finish_internal() to be called by psa_mac_finish() and
psa_mac_verify() in order to be able to check key usage separatly.
diff --git a/include/psa/crypto_struct.h b/include/psa/crypto_struct.h
index 8987840..eba4862 100644
--- a/include/psa/crypto_struct.h
+++ b/include/psa/crypto_struct.h
@@ -82,6 +82,8 @@
     int iv_required : 1;
     int iv_set : 1;
     int has_input : 1;
+    int key_usage_sign : 1;
+    int key_usage_verify : 1;
     uint8_t mac_size;
     union
     {