gpgtar,w32: Fix file size computation

* tools/gpgtar-create.c (fillup_entry_w32): Move parentheses.

The bug is so obvious that I wonder why it was not reported more often
on Windows. (Adding 1 to MAXDWORD (0xfffffff) always gives 0 for the
product).

• Fixes-commit: 8b8925a2bdbb12dd537dde20a27cdb1416c2f1ae
• Signed-off-by: Werner Koch <wk@gnupg.org>