xfrm: ifdef setsockopt(UDP_ENCAP_ESPINUDP/UDP_ENCAP_ESPINUDP_NON_IKE)

If IPsec is not configured, there is no reason to delay the inevitable.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>