Documentation/ABI: Add missed attribute for mlxreg-io sysfs interfaces

Add missed "cpld4_version" attribute.

Fixes: 52675da1 ("Documentation/ABI: Add new attribute for mlxreg-io sysfs interfaces")
Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Documentation/ABI/stable/sysfs-driver-mlxreg-io

@@ -121,6 +121,15 @@ Description:	These files show the system reset cause, as following: ComEx
 
 		The files are read only.
 
+What:		/sys/devices/platform/mlxplat/mlxreg-io/hwmon/hwmon*/cpld4_version
+Date:		November 2018
+KernelVersion:	5.0
+Contact:	Vadim Pasternak <vadimpmellanox.com>
+Description:	These files show with which CPLD versions have been burned
+		on LED board.
+
+		The files are read only.
+
 Date:		June 2019
 KernelVersion:	5.3
 Contact:	Vadim Pasternak <vadimpmellanox.com>