hwrng: pseries - constify vio_device_id

vio_device_id are not supposed to change at runtime. All functions
working with vio_device_id provided by <asm/vio.h> work with
const vio_device_id. So mark the non-const structs as const.
Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/pseries-rng.c

@@ -72,7 +72,7 @@ static int pseries_rng_remove(struct vio_dev *dev)
 	return 0;
 }
 
-static struct vio_device_id pseries_rng_driver_ids[] = {
+static const struct vio_device_id pseries_rng_driver_ids[] = {
 	{ "ibm,random-v1", "ibm,random"},
 	{ "", "" }
 };