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/Makefile b/drivers/iio/accel/Makefile
index 618488d..3f4a6d6 100644
--- a/drivers/iio/accel/Makefile
+++ b/drivers/iio/accel/Makefile
@@ -3,7 +3,8 @@
 #
 
 # When adding new entries keep the list in alphabetical order
-obj-$(CONFIG_ADXL345) += adxl345.o
+obj-$(CONFIG_ADXL345) += adxl345_core.o
+obj-$(CONFIG_ADXL345_I2C) += adxl345_i2c.o
 obj-$(CONFIG_BMA180) += bma180.o
 obj-$(CONFIG_BMA220) += bma220_spi.o
 obj-$(CONFIG_BMC150_ACCEL) += bmc150-accel-core.o