hwmon: (isl28022) document shunt voltage channel

During the upstreaming process, the driver has been extended to report
the shunt voltage as well. Document that.

Signed-off-by: Wolfram Sang <[email protected]>
Signed-off-by: Guenter Roeck <[email protected]>

Author: Wolfram Sang

Documentation/hwmon/isl28022.rst

@@ -48,6 +48,7 @@ The following attributes are supported. All attributes are read-only.
 
 ======================= =======================================================
 in0_input		bus voltage (milli Volt)
+in1_input		shunt voltage (milli Volt)
 
 curr1_input		current (milli Ampere)
 power1_input		power (micro Watt)