[nat] Slightly improve logging..

If we find the connection of a different BSC at least log the
BSCs that had duplicated references. We should also dump the
src ref and such but i am not doing this right now.
diff --git a/openbsc/src/nat/bsc_nat.c b/openbsc/src/nat/bsc_nat.c
index abf38ce..00dcc88 100644
--- a/openbsc/src/nat/bsc_nat.c
+++ b/openbsc/src/nat/bsc_nat.c
@@ -556,7 +556,8 @@
 	}
 
 	if (con && con->bsc != bsc) {
-		LOGP(DNAT, LOGL_ERROR, "Found the wrong entry.\n");
+		LOGP(DNAT, LOGL_ERROR, "The connection belongs to a different BTS: input: %d con: %d\n",
+		     bsc->cfg->nr, con->bsc->cfg->nr);
 		goto exit2;
 	}