usb: gadget: gadgetfs: fix an oops in ep_write()

We try to free an ERR_PTR on this error path.

Fixes: b44be2462dbe ('usb: gadget: gadgetfs: Free memory allocated by memdup_user()')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/legacy/inode.c

@@ -441,6 +441,7 @@ ep_write (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
 	kbuf = memdup_user(buf, len);
 	if (IS_ERR(kbuf)) {
 		value = PTR_ERR(kbuf);
+		kbuf = NULL;
 		goto free1;
 	}