*: add/cleanup initialisers

There were some (inconsequential) warnings about uninitialised use of
variables.  Also, in one case, sub-structs were mixed in initialisation,
which doesn't quite work as intended.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/ospfd/ospf_spf.c b/ospfd/ospf_spf.c
index 6205b3e..58a3992 100644
--- a/ospfd/ospf_spf.c
+++ b/ospfd/ospf_spf.c
@@ -590,7 +590,7 @@
 
           if (l->m[0].type == LSA_LINK_TYPE_POINTOPOINT)
             {
-	      struct in_addr nexthop;
+              struct in_addr nexthop = { .s_addr = 0 };
 
               /* If the destination is a router which connects to
                  the calculating router via a Point-to-MultiPoint