usb: gadget: move bind() callback back to struct usb_composite_driver

This partly reverts 07a18bd7 ("usb gadget: don't save bind callback in
struct usb_composite_driver") and fixes new drivers. The section missmatch
problems was solved by whitelisting structs in question via __ref.

Cc: devel@driverdev.osuosl.org
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/gadget/tcm_usb_gadget.c b/drivers/usb/gadget/tcm_usb_gadget.c
index 28fef844..35ca09a 100644
--- a/drivers/usb/gadget/tcm_usb_gadget.c
+++ b/drivers/usb/gadget/tcm_usb_gadget.c
@@ -2441,12 +2441,13 @@
 	.dev            = &usbg_device_desc,
 	.strings        = usbg_strings,
 	.max_speed      = USB_SPEED_SUPER,
+	.bind		= usb_target_bind,
 	.unbind         = guas_unbind,
 };
 
 static int usbg_attach(struct usbg_tpg *tpg)
 {
-	return usb_composite_probe(&usbg_driver, usb_target_bind);
+	return usb_composite_probe(&usbg_driver);
 }
 
 static void usbg_detach(struct usbg_tpg *tpg)