netdev: Remove redundant checks for CAP_NET_ADMIN in MDIO implementations

dev_ioctl() already checks capable(CAP_NET_ADMIN) before calling the
driver's implementation of MDIO ioctls.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/sis900.c

@@ -2128,8 +2128,6 @@ static int mii_ioctl(struct net_device *net_dev, struct ifreq *rq, int cmd)
 		return 0;
 
 	case SIOCSMIIREG:		/* Write MII PHY register. */
-		if (!capable(CAP_NET_ADMIN))
-			return -EPERM;
 		mdio_write(net_dev, data->phy_id & 0x1f, data->reg_num & 0x1f, data->val_in);
 		return 0;
 	default: