net: ethernet: ravb: constify bb_ops

The only usage of bb_ops is to assign its address to the ops field in
the mdiobb_ctrl struct, which is a const pointer. Make it const to allow
the compiler to put it in read-only memory.
Signed-off-by: NRikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/renesas/ravb_main.c

@@ -162,7 +162,7 @@ static int ravb_get_mdio_data(struct mdiobb_ctrl *ctrl)
 }
 
 /* MDIO bus control struct */
-static struct mdiobb_ops bb_ops = {
+static const struct mdiobb_ops bb_ops = {
 	.owner = THIS_MODULE,
 	.set_mdc = ravb_set_mdc,
 	.set_mdio_dir = ravb_set_mdio_dir,