net: renesas: sh_eth: 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: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/renesas/sh_eth.c

@@ -1202,7 +1202,7 @@ static void sh_mdc_ctrl(struct mdiobb_ctrl *ctrl, int bit)
 }
 
 /* mdio bus control struct */
-static struct mdiobb_ops bb_ops = {
+static const struct mdiobb_ops bb_ops = {
 	.owner = THIS_MODULE,
 	.set_mdc = sh_mdc_ctrl,
 	.set_mdio_dir = sh_mmd_ctrl,