iio: accel: adxl345: Split driver into core and I2C

Move I2C-specific code into its own file and rely on regmap to access
registers. The core code provides access to x, y, z and scale readings.

Signed-off-by: Eva Rachel Retuya <eraretuya@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
index 26b8614..a725227 100644
--- a/drivers/iio/accel/Kconfig
+++ b/drivers/iio/accel/Kconfig
@@ -6,16 +6,21 @@
 menu "Accelerometers"
 
 config ADXL345
-	tristate "Analog Devices ADXL345 3-Axis Digital Accelerometer Driver"
-	depends on !(INPUT_ADXL34X=y || INPUT_ADXL34X=m)
+	tristate
+
+config ADXL345_I2C
+	tristate "Analog Devices ADXL345 3-Axis Digital Accelerometer I2C Driver"
+	depends on INPUT_ADXL34X=n
 	depends on I2C
+	select ADXL345
 	select REGMAP_I2C
 	help
 	  Say Y here if you want to build support for the Analog Devices
 	  ADXL345 3-axis digital accelerometer.
 
-	  To compile this driver as a module, choose M here: the
-	  module will be called adxl345.
+	  To compile this driver as a module, choose M here: the module
+	  will be called adxl345_i2c and you will also get adxl345_core
+	  for the core module.
 
 config BMA180
 	tristate "Bosch BMA180/BMA250 3-Axis Accelerometer Driver"