ath6kl: 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: Steve deRosier <derosier@gmail.com>
Tested-by: Steve deRosier <derosier@gmail.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath6kl/usb.c

@@ -1201,7 +1201,7 @@ static int ath6kl_usb_pm_resume(struct usb_interface *interface)
 #endif
 
 /* table of devices that work with this driver */
-static struct usb_device_id ath6kl_usb_ids[] = {
+static const struct usb_device_id ath6kl_usb_ids[] = {
 	{USB_DEVICE(0x0cf3, 0x9375)},
 	{USB_DEVICE(0x0cf3, 0x9374)},
 	{ /* Terminating entry */ },