net: usb: cdc-phonet: constify usb_device_id

usb_device_id are not supposed to change at runtime. All functions
working with usb_device_id provided by <linux/usb.h> work with
const usb_device_id. So mark the non-const structs as const.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/cdc-phonet.c

@@ -304,7 +304,7 @@ static void usbpn_setup(struct net_device *dev)
 /*
  * USB driver callbacks
  */
-static struct usb_device_id usbpn_ids[] = {
+static const struct usb_device_id usbpn_ids[] = {
 	{
 		.match_flags = USB_DEVICE_ID_MATCH_VENDOR
 			| USB_DEVICE_ID_MATCH_INT_CLASS