util: Use designated initializers to clean up the format tables' pack/unpack.

The generated .c had a bunch of NULLs and notes for what kind of function
was being skipped, when we can just skip them by filling in the fields
with names.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5728>
1 file changed