newEndpoint no longer references *Device, but receives individual values

extracted from the device. Makes testing easier.

usb/endpoint.go

@@ -78,12 +78,12 @@ func (e *endpoint) transfer(buf []byte, timeout time.Duration) (int, error) {
 	return n, nil
 }
 
-func newEndpoint(d *Device, s InterfaceSetup, e EndpointInfo) *endpoint {
+func newEndpoint(h *libusbDevHandle, s InterfaceSetup, e EndpointInfo, rt, wt time.Duration) *endpoint {
 	return &endpoint{
 		InterfaceSetup: s,
 		EndpointInfo:   e,
-		h:              d.handle,
-		readTimeout:    d.ReadTimeout,
-		writeTimeout:   d.WriteTimeout,
+		h:              h,
+		readTimeout:    rt,
+		writeTimeout:   wt,
 	}
 }