ALSA: 6fire: 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: Takashi Iwai <tiwai@suse.de>

sound/usb/6fire/chip.c

@@ -198,7 +198,7 @@ static void usb6fire_chip_disconnect(struct usb_interface *intf)
 	}
 }
 
-static struct usb_device_id device_table[] = {
+static const struct usb_device_id device_table[] = {
 	{
 		.match_flags = USB_DEVICE_ID_MATCH_DEVICE,
 		.idVendor = 0x0ccd,