iio: pressure: bmp280: Fix alignment for DMA safety

Adds DMA-safe buffers to driver data struct to store raw data from sensors

The multiple buffers used thorough the driver share the same memory
allocated as part of the device data instance. The union containing
the buffers is aligned to allow safe usage with DMA operations, such
as regmap bulk read calls.

Updated measurement and calibration reading functions to use the safe
DMA buffers.
Suggested-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Angel Iglesias <ang.iglesiasg@gmail.com>
Link: https://lore.kernel.org/r/7919793f7f63224d5ce413c66d648029683c17ac.1663025017.git.ang.iglesiasg@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/pressure/bmp280.h

@@ -13,8 +13,8 @@
 #define BMP280_REG_PRESS_LSB		0xF8
 #define BMP280_REG_PRESS_MSB		0xF7
 
-/* Helper mask to truncate excess 12 bits on pressure and temp readings */
-#define BMP280_MEAS_TRIM_MASK		GENMASK(31, 12)
+/* Helper mask to truncate excess 4 bits on pressure and temp readings */
+#define BMP280_MEAS_TRIM_MASK		GENMASK(24, 4)
 
 #define BMP280_REG_CONFIG		0xF5
 #define BMP280_REG_CTRL_MEAS		0xF4