usb: gadget: udc: fix NULL dereference in remove()

The "udc" pointer was never set in the probe() function so it will
lead to a NULL dereference in udc_pci_remove() when we do:

	usb_del_gadget_udc(&udc->gadget);
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/ZG+A/dNpFWAlCChk@kiliSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/udc/amd5536udc_pci.c

@@ -170,6 +170,9 @@ static int udc_pci_probe(
 		retval = -ENODEV;
 		goto err_probe;
 	}
+
+	udc = dev;
+
 	return 0;
 
 err_probe: