iio: light: Add support for Sensortek STK3310

Minimal implementation of an IIO driver for the Sensortek
STK3310 ambient light and proximity sensor. The STK3311
model is also supported.

Includes:
- ACPI support;
- read_raw and write_raw;
- reading and setting configuration parameters for gain/scale
  and integration time for both ALS and PS.
- power management

Signed-off-by: Tiberiu Breana <tiberiu.a.breana@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/Kconfig

@@ -175,6 +175,17 @@ config LTR501
 	 This driver can also be built as a module.  If so, the module
          will be called ltr501.
 
+config STK3310
+	tristate "STK3310 ALS and proximity sensor"
+	depends on I2C
+	help
+	 Say yes here to get support for the Sensortek STK3310 ambient light
+	 and proximity sensor. The STK3311 model is also supported by this
+	 driver.
+
+	 Choosing M will build the driver as a module. If so, the module
+	 will be called stk3310.
+
 config TCS3414
 	tristate "TAOS TCS3414 digital color sensor"
 	depends on I2C

drivers/iio/light/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_JSA1212)		+= jsa1212.o
 obj-$(CONFIG_SENSORS_LM3533)	+= lm3533-als.o
 obj-$(CONFIG_LTR501)		+= ltr501.o
 obj-$(CONFIG_SENSORS_TSL2563)	+= tsl2563.o
+obj-$(CONFIG_STK3310)          += stk3310.o
 obj-$(CONFIG_TCS3414)		+= tcs3414.o
 obj-$(CONFIG_TCS3472)		+= tcs3472.o
 obj-$(CONFIG_TSL4531)		+= tsl4531.o