ospfd: Make ospf_if_lookup_recv_if() find the right unnumbered i/f

ospfd: Make ospf_if_lookup_recv_if() find the right unnumbered i/f

This function will return the interface for the first matching
remote address for PtP i/f's. That won't work for multiple
unnumbered i/f's as these may all have the same address.

Pass in the struct interface pointer, ifp, to find the
correct set of oi's to search in. This also reduces the
size of the search list, making it faster.

* ospfd/ospf_interface.c: Add struct interface * param to
  ospf_if_lookup_recv_if() to select the right list to search in.
* ospfd/ospf_interface.h: ditto.
* ospfd/ospf_packet.c: Pass new ifp argument to ospf_if_lookup_recv_if()