usb: cdnsp: Mark cdnsp_gadget_ops with static keyword

Fix the following sparse warning:

drivers/usb/cdns3/cdnsp-gadget.c:1546:29: warning: symbol 'cdnsp_gadget_ops' was not declared. Should it be static?
Signed-off-by: Zou Wei <zou_wei@huawei.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>

drivers/usb/cdns3/cdnsp-gadget.c

@@ -1543,7 +1543,7 @@ static int cdnsp_gadget_pullup(struct usb_gadget *gadget, int is_on)
 	return 0;
 }
 
-const struct usb_gadget_ops cdnsp_gadget_ops = {
+static const struct usb_gadget_ops cdnsp_gadget_ops = {
 	.get_frame		= cdnsp_gadget_get_frame,
 	.wakeup			= cdnsp_gadget_wakeup,
 	.set_selfpowered	= cdnsp_gadget_set_selfpowered,