regulator: mpq7920: Check the correct variable in mpq7920_regulator_register()

There is a typo in the error checking.  We should be checking
"->rdev[i]" instead of just "->rdev".

Fixes: 6501c1f5 ("regulator: mpq7920: add mpq7920 regulator driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200113125805.xri6jqoxy2ldzqyg@kili.mountainSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/mpq7920.c

@@ -274,8 +274,8 @@ static inline int mpq7920_regulator_register(
 
 		info->rdev[i] = devm_regulator_register(info->dev, rdesc,
 					 config);
-		if (IS_ERR(info->rdev))
-			return PTR_ERR(info->rdev);
+		if (IS_ERR(info->rdev[i]))
+			return PTR_ERR(info->rdev[i]);
 	}
 
 	return 0;