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 <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Signed-off-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

drivers/watchdog/pcwd_usb.c

···
 #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 */
 };