vxlan: Bump error counters for header mismatches

The VXLAN driver so far has not increased the error counters for packets
that set reserved bits. It does so for other packet errors, so do it for
this case as well.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/d096084167d56706d620afe5136cf37a2d34d1b9.1733412063.git.petrm@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>