vxlan: vxlan_rcv(): Drop unparsed

The code currently validates the VXLAN header in two ways: first by
comparing it with the set of reserved bits, constructed ahead of time
during the netdevice construction; and second by gradually clearing the
bits off a separate copy of VXLAN header, "unparsed". Drop the latter
validation method.

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/4559f16c5664c189b3a4ee6f5da91f552ad4821c.1733412063.git.petrm@nvidia.com


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