iio: sps30: 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 `cleaning_period` device attribute of
the sps30 driver.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20211216185217.1054495-14-lars@metafoo.deSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/chemical/sps30.c

@@ -221,7 +221,7 @@ static ssize_t cleaning_period_show(struct device *dev,
 	if (ret)
 		return ret;
 
-	return sprintf(buf, "%d\n", be32_to_cpu(val));
+	return sysfs_emit(buf, "%d\n", be32_to_cpu(val));
 }
 
 static ssize_t cleaning_period_store(struct device *dev, struct device_attribute *attr,