lwtunnel: add options process for arp request

Without options copied to the dst tun_info in iptunnel_metadata_reply()
called by arp_process for handling arp_request, the generated arp_reply
packet may be dropped or sent out with wrong options for some tunnels
like erspan and vxlan, and the traffic will break.

Fixes: 63d008a4

 ("ipv4: send arp replies to the correct tunnel")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>