iio: accel: Add support for Sensortek STK8BA50

Minimal implementation of an IIO driver for the Sensortek
STK8BA50 3-axis accelerometer. Datasheet:
http://szgsensor.com/uploads/soft/141229/STK8BA50%D2%E5%BC%CE.pdf

Includes:
- ACPI support;
- read_raw for x,y,z axes;
- reading and setting the scale (range) parameter.
- power management

Signed-off-by: Tiberiu Breana <tiberiu.a.breana@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
index 8bd8ccb..00e7bcb 100644
--- a/drivers/iio/accel/Kconfig
+++ b/drivers/iio/accel/Kconfig
@@ -147,4 +147,14 @@
 	  Choosing M will build the driver as a module. If so, the module
 	  will be called stk8312.
 
+config STK8BA50
+	tristate "Sensortek STK8BA50 3-Axis Accelerometer Driver"
+	depends on I2C
+	help
+	  Say yes here to get support for the Sensortek STK8BA50 3-axis
+	  accelerometer.
+
+	  Choosing M will build the driver as a module. If so, the module
+	  will be called stk8ba50.
+
 endmenu