Add support for Accton as9726-32d platform
This pull request is based on as9716-32d, so I reference as9716-32d to create new model: as9726-32d.
This module do not need led driver to control led, FPGA can handle it.
I also implement API2.0(sonic_platform) for this model, CPLD driver, PSU driver, Fan driver to control these HW behavior.
