iio: max31856: Use sysfs_emit()

sysfs_emit() is preferred over raw s*printf() for sysfs attributes since it
knows about the sysfs buffer specifics and has some built-in checks for
size and alignment.

Use sysfs_emit() to format the custom `fault_ovuv`, `fault_oc` and
`in_temp_filter_notch_center_frequency` device attributes of the max31856
driver.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20211216185217.1054495-9-lars@metafoo.deSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/temperature/max31856.c

@@ -320,7 +320,7 @@ static ssize_t show_fault(struct device *dev, u8 faultbit, char *buf)
 
 	fault = reg_val & faultbit;
 
-	return sprintf(buf, "%d\n", fault);
+	return sysfs_emit(buf, "%d\n", fault);
 }
 
 static ssize_t show_fault_ovuv(struct device *dev,
@@ -344,7 +344,7 @@ static ssize_t show_filter(struct device *dev,
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct max31856_data *data = iio_priv(indio_dev);
 
-	return sprintf(buf, "%d\n", data->filter_50hz ? 50 : 60);
+	return sysfs_emit(buf, "%d\n", data->filter_50hz ? 50 : 60);
 }
 
 static ssize_t set_filter(struct device *dev,