video: fbdev: udlfb: 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>
Cc: Steve Glendinning <steve.glendinning@shawell.net>
Cc: Bernie Thompson <bernie@plugable.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

drivers/video/fbdev/udlfb.c

@@ -54,7 +54,7 @@ static const u32 udlfb_info_flags = FBINFO_DEFAULT | FBINFO_READS_FAST |
  * which is compatible with all known USB 2.0 era graphics chips and firmware,
  * but allows DisplayLink to increment those for any future incompatible chips
  */
-static struct usb_device_id id_table[] = {
+static const struct usb_device_id id_table[] = {
 	{.idVendor = 0x17e9,
 	 .bInterfaceClass = 0xff,
 	 .bInterfaceSubClass = 0x00,