usb: gadget: gr_udc: Make of_device_id array const

Make of_device_id array const, because all OF functions handle
it as const.
Acked-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/gr_udc.c

@@ -2212,7 +2212,7 @@ static int gr_probe(struct platform_device *pdev)
 	return retval;
 }
 
-static struct of_device_id gr_match[] = {
+static const struct of_device_id gr_match[] = {
 	{.name = "GAISLER_USBDC"},
 	{.name = "01_021"},
 	{},