usb: gadget: amd5536udc: use WARN_ON

Use WARN_ON() instead of halting the kernel with BUG_ON() and also fix
the checkpatch warning.

Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/gadget/udc/amd5536udc.c b/drivers/usb/gadget/udc/amd5536udc.c
index 3f85044..6223b1b 100644
--- a/drivers/usb/gadget/udc/amd5536udc.c
+++ b/drivers/usb/gadget/udc/amd5536udc.c
@@ -3127,7 +3127,8 @@
 
 	usb_del_gadget_udc(&udc->gadget);
 	/* gadget driver must not be registered */
-	BUG_ON(dev->driver != NULL);
+	if (WARN_ON(dev->driver))
+		return;
 
 	/* dma pool cleanup */
 	if (dev->data_requests)