odp-util: Avoid reading wrong table in generate_all_wildcard_mask().

odp-util: Avoid reading wrong table in generate_all_wildcard_mask().

These lines of code are intended to copy the 'next' and 'next_max' members
of tbl[type] into local variables 'tbl' and 'max':
            tbl = tbl[type].next;
            max = tbl[type].next_max;
They didn't do it properly because the first line changes 'tbl', so that
the first and seconds lines' references to tbl[type] refer to different
objects.

This commit fixes the problem.

Found by libfuzzer.

Reported-by: Bhargava Shastry <bshastry@sec.t-labs.tu-berlin.de>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Justin Pettit <jpettit@ovn.org>