vxlan: remove redundant conversion of vni in vxlan_nl2conf

The IFLA_VXLAN_ID data has been converted to local variable vni in
vxlan_nl2conf(), there is no need to do it again when set conf->vni.

Signed-off-by: Wang Liang <wangliang74@huawei.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Link: https://patch.msgid.link/20250722093049.1527505-1-wangliang74@huawei.com


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