watchdog: pcwd_usb: 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>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/pcwd_usb.c

@@ -74,7 +74,7 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
 #define USB_PCWD_PRODUCT_ID	0x1140
 
 /* table of devices that work with this driver */
-static struct usb_device_id usb_pcwd_table[] = {
+static const struct usb_device_id usb_pcwd_table[] = {
 	{ USB_DEVICE(USB_PCWD_VENDOR_ID, USB_PCWD_PRODUCT_ID) },
 	{ }					/* Terminating entry */
 };