iio: pressure: bmp280: BMP280 calibration to entropy

The BMP280/BME280 calibration data should also go into the
entropy pool, like we do for BMP180.

This just adds the temperature and pressure calibration, the
humidity calibration seems like too much annoying calls to
add.

Cc: Tomasz Duszynski <tduszyns@gmail.com>
Cc: Stefan Tatschner <stefan.tatschner@gmail.com>
Cc: Andreas Klinger <ak@it-klinger.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/pressure/bmp280-core.c

@@ -164,6 +164,9 @@ static int bmp280_read_calib(struct bmp280_data *data,
 		return ret;
 	}
 
+	/* Toss the temperature calibration data into the entropy pool */
+	add_device_randomness(t_buf, sizeof(t_buf));
+
 	calib->T1 = le16_to_cpu(t_buf[T1]);
 	calib->T2 = le16_to_cpu(t_buf[T2]);
 	calib->T3 = le16_to_cpu(t_buf[T3]);
@@ -177,6 +180,9 @@ static int bmp280_read_calib(struct bmp280_data *data,
 		return ret;
 	}
 
+	/* Toss the pressure calibration data into the entropy pool */
+	add_device_randomness(p_buf, sizeof(p_buf));
+
 	calib->P1 = le16_to_cpu(p_buf[P1]);
 	calib->P2 = le16_to_cpu(p_buf[P2]);
 	calib->P3 = le16_to_cpu(p_buf[P3]);