net: irda: mcs7780: 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: NArvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/irda/mcs7780.c

@@ -66,7 +66,7 @@
 #define MCS_VENDOR_ID 0x9710
 #define MCS_PRODUCT_ID 0x7780
 
-static struct usb_device_id mcs_table[] = {
+static const struct usb_device_id mcs_table[] = {
 	/* MosChip Corp.,  MCS7780 FIR-USB Adapter */
 	{USB_DEVICE(MCS_VENDOR_ID, MCS_PRODUCT_ID)},
 	{},