MDEV-9175 Query parser tansforms MICROSECOND into SECOND_FRAC, which does not work

mysql-test/r/second_frac-9175.result

+select timestampdiff(microsecond,'2000-01-01 00:00:00','2001-01-01 00:00:00.123456');
+timestampdiff(microsecond,'2000-01-01 00:00:00','2001-01-01 00:00:00.123456')
+31622400123456
+explain extended select timestampdiff(microsecond,'2000-01-01 00:00:00','2001-01-01 00:00:00.123456');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+Warnings:
+Note	1003	select timestampdiff(MICROSECOND,'2000-01-01 00:00:00','2001-01-01 00:00:00.123456') AS `timestampdiff(microsecond,'2000-01-01 00:00:00','2001-01-01 00:00:00.123456')`
+create view v1 as select timestampdiff(microsecond,'2000-01-01 00:00:00','2001-01-01 00:00:00.123456');
+select * from v1;
+Name_exp_1
+31622400123456
+drop view v1;

mysql-test/t/second_frac-9175.test

+#
+# MDEV-9175 Query parser tansforms MICROSECOND into SECOND_FRAC, which does not work
+#
+
+select timestampdiff(microsecond,'2000-01-01 00:00:00','2001-01-01 00:00:00.123456');
+explain extended select timestampdiff(microsecond,'2000-01-01 00:00:00','2001-01-01 00:00:00.123456');
+create view v1 as select timestampdiff(microsecond,'2000-01-01 00:00:00','2001-01-01 00:00:00.123456');
+select * from v1;
+drop view v1;

sql/item_timefunc.cc

@@ -2916,7 +2916,7 @@ void Item_func_timestamp_diff::print(String *str, enum_query_type query_type)
     str->append(STRING_WITH_LEN("SECOND"));
     break;		
   case INTERVAL_MICROSECOND:
-    str->append(STRING_WITH_LEN("SECOND_FRAC"));
+    str->append(STRING_WITH_LEN("MICROSECOND"));
     break;
   default:
     break;