Fix weasel infiniband interface name

Reviewed-by: Rodrigo Arias Mallo <rodrigo.arias@bsc.es>

m/weasel/configuration.nix

@@ -25,7 +25,7 @@
       address = "10.0.40.6";
       prefixLength = 24;
     } ];
-    interfaces.ibp5s0.ipv4.addresses = [ {
+    interfaces.ibs785.ipv4.addresses = [ {
       address = "10.0.42.6";
       prefixLength = 24;
     } ];