vxlan: Drop 'changelink' parameter from vxlan_dev_configure()

vxlan_dev_configure() only has a single caller that passes false
for the changelink parameter. Drop the parameter and inline the
sole value.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>