vxlan: vxlan_rcv() callees: Drop the unparsed argument

vxlan: vxlan_rcv() callees: Drop the unparsed argument

The functions vxlan_remcsum() and vxlan_parse_gbp_hdr() take both the SKB
and the unparsed VXLAN header. Now that unparsed adjustment is handled
directly by vxlan_rcv(), drop this argument, and have the function derive
it from the SKB on its own.

vxlan_parse_gpe_proto() does not take SKB, so keep the header parameter.
However const it so that it's clear that the intention is that it does not
get changed.

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/5ea651f4e06485ba1a84a8eb556a457c39f0dfd4.1733412063.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>