MDEV-32144 Debug assertion failure w == MAYBE_NOP in mtr_t::memcpy()

trx_undo_write_trx_xid(): Silence the debug assertion by passing
a template parameter that causes us to not care that the contents of
the page did not actually change and no log record would be written.
This debug assertion could fail if XA PREPARE was executed multiple
times with the same XID.

storage/innobase/trx/trx0undo.cc

@@ -458,9 +458,9 @@ static uint16_t trx_undo_header_create(buf_block_t *undo_page, trx_id_t trx_id,
   mach_write_to_2(buf + 2, free);
   static_assert(TRX_UNDO_STATE + 2 == TRX_UNDO_LAST_LOG, "compatibility");
   static_assert(!((TRX_UNDO_SEG_HDR + TRX_UNDO_STATE) % 4), "alignment");
-  mtr->memcpy(*undo_page, my_assume_aligned<4>
-              (TRX_UNDO_SEG_HDR + TRX_UNDO_STATE + undo_page->frame),
-              buf, 4);
+  mtr->memcpy<mtr_t::MAYBE_NOP>
+    (*undo_page, my_assume_aligned<4>
+     (TRX_UNDO_SEG_HDR + TRX_UNDO_STATE + undo_page->frame), buf, 4);
   if (prev_log)
     mtr->write<2>(*undo_page, prev_log + TRX_UNDO_NEXT_LOG + undo_page->frame,
                   free);