device: remove unused fields from DummyDatagram and DummyBind

Signed-off-by: Josh Bleecher Snyder <[email protected]>

Author: josharian

device/bind_test.go

@@ -14,14 +14,11 @@ import (
 type DummyDatagram struct {
 	msg      []byte
 	endpoint conn.Endpoint
-	world    bool // better type
 }
 
 type DummyBind struct {
 	in6    chan DummyDatagram
-	ou6    chan DummyDatagram
 	in4    chan DummyDatagram
-	ou4    chan DummyDatagram
 	closed bool
 }