usb: gadget: hid: Convert to use list_count()

The list API now provides the list_count() to help with counting
existing nodes in the list. Utilise it.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20221123144901.40493-2-andriy.shevchenko@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/legacy/hid.c

@@ -133,14 +133,11 @@ static struct usb_configuration config_driver = {
 static int hid_bind(struct usb_composite_dev *cdev)
 {
 	struct usb_gadget *gadget = cdev->gadget;
-	struct list_head *tmp;
 	struct hidg_func_node *n = NULL, *m, *iter_n;
 	struct f_hid_opts *hid_opts;
-	int status, funcs = 0;
-
-	list_for_each(tmp, &hidg_func_list)
-		funcs++;
+	int status, funcs;
 
+	funcs = list_count(&hidg_func_list);
 	if (!funcs)
 		return -ENODEV;