staging:iio:light: drop stale ABI docs

There are no remaining light drivers in staging/iio.
The content of this file are either included in the non staging
ABI docs, or don't seem to be used in any current driver.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20200905174721.216452-4-jic23@kernel.org

drivers/staging/iio/Documentation/sysfs-bus-iio-light

-What:		/sys/bus/iio/devices/device[n]/in_illuminance0[_input|_raw]
-KernelVersion:	2.6.35
-Contact:	linux-iio@vger.kernel.org
-Description:
-		This should return the calculated lux from the light sensor. If
-		it comes back in SI units, it should also include _input else it
-		should include _raw to signify it is not in SI units.
-
-What:		/sys/.../device[n]/proximity_on_chip_ambient_infrared_suppression
-KernelVersion:	2.6.37
-Contact:	linux-iio@vger.kernel.org
-Description:
-		Hardware dependent mode for an ALS device to calculate the value
-		in proximity mode. When this is enabled, then the device should
-		use a infrared sensor reading to remove infrared noise from the
-		proximity reading. If this is not enabled, the driver can still
-		do this calculation manually by reading the infrared sensor
-		value and doing the negation in sw.
-
-What:		/sys/bus/iio/devices/device[n]/in_proximity[_input|_raw]
-KernelVersion:	2.6.37
-Contact:	linux-iio@vger.kernel.org
-Description:
-		This property is supported by proximity sensors and should be
-		used to return the value of a reading by the sensor. If this
-		value is returned in SI units, it should also include _input
-		but if it is not, then it should include _raw.
-
-What:		/sys/bus/iio/devices/device[n]/intensity_infrared[_input|_raw]
-KernelVersion:	2.6.37
-Contact:	linux-iio@vger.kernel.org
-Description:
-		This property is supported by sensors that have an infrared
-		sensing mode. This value should be the output from a reading
-		and if expressed in SI units, should include _input. If this
-		value is not in SI units, then it should include _raw.
-
-What:		/sys/bus/iio/devices/device[n]/in_illuminance0_target
-KernelVersion:	2.6.37
-Contact:	linux-iio@vger.kernel.org
-Description:
-		This property gets/sets the last known external
-		lux measurement used in/for calibration.
-
-What:		/sys/bus/iio/devices/device[n]/in_illuminance0_integration_time
-KernelVersion:	2.6.37
-Contact:	linux-iio@vger.kernel.org
-Description:
-		This property gets/sets the sensors ADC analog integration time.
-
-What:		/sys/bus/iio/devices/device[n]/in_illuminance0_lux_table
-KernelVersion:	2.6.37
-Contact:	linux-iio@vger.kernel.org
-Description:
-		This property gets/sets the table of coefficients
-		used in calculating illuminance in lux.
-
-What:		/sys/bus/iio/devices/device[n]/in_intensity_clear[_input|_raw]
-What:		/sys/bus/iio/devices/device[n]/in_intensity_red[_input|_raw]
-What:		/sys/bus/iio/devices/device[n]/in_intensity_green[_input|_raw]
-What:		/sys/bus/iio/devices/device[n]/in_intensity_blue[_input|_raw]
-KernelVersion:	3.6.0
-Contact:	linux-iio@vger.kernel.org
-Description:
-		This property is supported by sensors that have a RGBC
-		sensing mode. This value should be the output from a reading
-		and if expressed in SI units, should include _input. If this
-		value is not in SI units (irradiance, uW/mm^2), then it should
-		include _raw.
-
-What:		/sys/bus/iio/devices/device[n]/in_cct0[_input|_raw]
-KernelVersion:	3.6.0
-Contact:	linux-iio@vger.kernel.org
-Description:
-		This should return the correlated color temperature from the
-		light sensor. If it comes back in SI units, it should also
-		include _input else it should include _raw to signify it is not
-		in SI units.
-