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

commit f3efc406 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>