[platform/device] - Implement Silverstone platform API [PSU]

[mudsut4ke]

- What I did

• Implement part of the Chassis and Fan related APIs.

• Psu APIs

  • get_voltage()
  • get_current()
  • get_power()
  • get_powergood_status()
  • set_status_led()
  • get_status_led()

• Update Fan APIs to support PSU FAN

  • get_direction()
  • get_speed()
  • get_target_speed()
  • get_speed_tolerance()
  • get_target_speed()

• PSU APIs base on Device API

  • get_name()
  • get_presence()
  • get_model()
  • get_serial()
  • get_status()

- How I did it

1. Implement PSU APIs
2. Update FAN API to support PSU Fans
3. Add PSU object to Chassis API

- How to verify it

• Write python script follow the new platform API design doc to verify it (Add design doc for new platform management API SONiC#285.)
• Test log: psu_api_silverstone_test.log

Signed-off-by: Wirut Getbamrung [email protected]