iio: adc: ad-sigma-delta: Document ABI for sigma delta adc

Add common calibration nodes for sigma delta adc.

Signed-off-by: Guillaume Ranquet <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

Documentation/ABI/testing/sysfs-bus-iio-adc-ad-sigma-delta

···
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_sys_calibration
+KernelVersion: 5.5
+Contact:	[e-mail]
+Description:
+		This attribute, if available, initiates the system calibration procedure. This is done on a
+		single channel at a time. Write '1' to start the calibration.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_sys_calibration_mode_available
+KernelVersion: 5.5
+Contact:	[e-mail]
+Description:
+		This attribute, if available, returns a list with the possible calibration modes.
+		There are two available options:
+		"zero_scale" - calibrate to zero scale
+		"full_scale" - calibrate to full scale
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_sys_calibration_mode
+KernelVersion: 5.5
+Contact:	[e-mail]
+Description:
+		This attribute, if available, sets up the calibration mode used in the system calibration
+		procedure. Reading returns the current calibration mode.
+		Writing sets the system calibration mode.

Documentation/ABI/testing/sysfs-bus-iio-adc-ad7192

···
 		the bridge can be disconnected (when it is not being used
 		using the bridge_switch_en attribute.
 
-What:		/sys/bus/iio/devices/iio:deviceX/in_voltagex_sys_calibration
-KernelVersion:
-Contact:	[e-mail]
-Description:
-		Initiates the system calibration procedure. This is done on a
-		single channel at a time. Write '1' to start the calibration.
-
 What:		/sys/bus/iio/devices/iio:deviceX/in_voltage2-voltage2_shorted_raw
 KernelVersion:
 Contact:	[e-mail]
 Description:
 		Measure voltage from AIN2 pin connected to AIN(+)
 		and AIN(-) shorted.
-
-What:		/sys/bus/iio/devices/iio:deviceX/in_voltagex_sys_calibration_mode_available
-KernelVersion:
-Contact:	[e-mail]
-Description:
-		Reading returns a list with the possible calibration modes.
-		There are two available options:
-		"zero_scale" - calibrate to zero scale
-		"full_scale" - calibrate to full scale
-
-What:		/sys/bus/iio/devices/iio:deviceX/in_voltagex_sys_calibration_mode
-KernelVersion:
-Contact:	[e-mail]
-Description:
-		Sets up the calibration mode used in the system calibration
-		procedure. Reading returns the current calibration mode.
-		Writing sets the system calibration mode.