drivers: ethernet: vsc8541: add MDIO enable/disable

The driver was not enabling the MDIO bus before trying to access
registers. Added enabling and disabling the bus around PHY register
accesses.

Signed-off-by: Robert Hancock <robert.hancock@calian.com>

Author: robhancocksed

drivers/ethernet/phy/phy_microchip_vsc8541.c

@@ -484,17 +484,21 @@ static int phy_mc_vsc8541_read(const struct device *dev, uint16_t reg_addr, uint
 	/* mask out lower byte */
 	reg_addr &= 0x00ff;
 
+	mdio_bus_enable(cfg->mdio_dev);
+
 	/* select page, given by register upper byte */
 	if (dev_data->active_page != page) {
 		ret = mdio_write(cfg->mdio_dev, cfg->addr, PHY_REG_PAGE_SELECTOR, (uint16_t)page);
 		if (ret) {
+			mdio_bus_disable(cfg->mdio_dev);
 			return ret;
 		}
 		dev_data->active_page = (int)page;
 	}
 
 	/* select register, given by register lower byte */
 	ret = mdio_read(cfg->mdio_dev, cfg->addr, reg_addr, (uint16_t *)data);
+	mdio_bus_disable(cfg->mdio_dev);
 	if (ret) {
 		return ret;
 	}
@@ -522,17 +526,21 @@ static int phy_mc_vsc8541_write(const struct device *dev, uint16_t reg_addr, uin
 	/* mask out lower byte */
 	reg_addr &= 0x00ff;
 
+	mdio_bus_enable(cfg->mdio_dev);
+
 	/* select page, given by register upper byte */
 	if (dev_data->active_page != page) {
 		ret = mdio_write(cfg->mdio_dev, cfg->addr, PHY_REG_PAGE_SELECTOR, (uint16_t)page);
 		if (ret) {
+			mdio_bus_disable(cfg->mdio_dev);
 			return ret;
 		}
 		dev_data->active_page = (int)page;
 	}
 
 	/* write register, given by lower byte */
 	ret = mdio_write(cfg->mdio_dev, cfg->addr, reg_addr, (uint16_t)data);
+	mdio_bus_disable(cfg->mdio_dev);
 	if (ret) {
 		return ret;
 	}