vxlan: Relocate assignment of default remote device

The default FDB entry can be associated with a net device if a physical
device (i.e., 'dev PHYS_DEV') was specified during the creation of the
VXLAN device.

The assignment of the net device pointer to 'dst->remote_dev' logically
belongs in the if block that resolves the pointer from the specified
ifindex, so move it there.

Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20250415121143.345227-6-idosch@nvidia.com


Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>