iio:bma180: Add BMA250 chip support

the BMA250 has only 10-bit resolution; while the data readout registers
have identical layout, the configuration is completely different compared
to the BMA180

datasheet: http://ae-bst.resource.bosch.com/media/products/dokumente/bma250/BST-BMA250-DS002-05.pdfSigned-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Cc: Oleksandr Kravchenko <o.v.kravchenko@globallogic.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/accel/Kconfig

@@ -6,13 +6,13 @@
 menu "Accelerometers"
 
 config BMA180
-	tristate "Bosch BMA180 3-Axis Accelerometer Driver"
+	tristate "Bosch BMA180/BMA250 3-Axis Accelerometer Driver"
 	depends on I2C
 	select IIO_BUFFER
 	select IIO_TRIGGERED_BUFFER
 	help
-	  Say Y here if you want to build a driver for the Bosch BMA180
-	  triaxial acceleration sensor.
+	  Say Y here if you want to build a driver for the Bosch BMA180 or
+	  BMA250 triaxial acceleration sensor.
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called bma180.