usb: gadget: move bind() callback back to struct usb_gadget_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 bind callback in modpost.

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/composite.c b/drivers/usb/gadget/composite.c
index 071d15c..2a345f2 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -1585,6 +1585,7 @@
 /*-------------------------------------------------------------------------*/
 
 static struct usb_gadget_driver composite_driver = {
+	.bind		= composite_bind,
 	.unbind		= composite_unbind,
 
 	.setup		= composite_setup,
@@ -1631,7 +1632,7 @@
 	composite_driver.max_speed = driver->max_speed;
 	composite = driver;
 
-	return usb_gadget_probe_driver(&composite_driver, composite_bind);
+	return usb_gadget_probe_driver(&composite_driver);
 }
 
 /**