regmap: mdio: Don't modify output if error happened

regmap_mdio_read() breaks the principle of "no touch output till it's known
that the operation succeeds". Refactor it accordingly.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210520120518.30490-1-andriy.shevchenko@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/base/regmap/regmap-mdio.c

@@ -11,9 +11,11 @@ static int regmap_mdio_read(void *context, unsigned int reg, unsigned int *val)
 	int ret;
 
 	ret = mdiobus_read(mdio_dev->bus, mdio_dev->addr, reg);
-	*val = ret & 0xffff;
+	if (ret < 0)
+		return ret;
 
-	return ret < 0 ? ret : 0;
+	*val = ret & 0xffff;
+	return 0;
 }
 
 static int regmap_mdio_write(void *context, unsigned int reg, unsigned int val)