MINOR: sock: make sock_find_compatible_fd() only take a receiver

We don't need to have a listener anymore to find an fd, a receiver with
its settings properly set is enough now.
diff --git a/src/proto_uxst.c b/src/proto_uxst.c
index 5cabea2..6691e85 100644
--- a/src/proto_uxst.c
+++ b/src/proto_uxst.c
@@ -113,7 +113,7 @@
 		goto bound;
 
 	if (listener->rx.fd == -1)
-		listener->rx.fd = sock_find_compatible_fd(listener);
+		listener->rx.fd = sock_find_compatible_fd(&listener->rx);
 	path = ((struct sockaddr_un *)&listener->rx.addr)->sun_path;
 
 	maxpathlen = MIN(MAXPATHLEN, sizeof(addr.sun_path));