Add support for Iris Ohyama SMT-PL1 smart plug (0x756B)

[hungyao]

The Iris Ohyama SMT-PL1 smart plug is identified as SP4M-JP in the Broadlink app, and through testing with the python-broadlink API (identified as 0x756B), works with the sp4 module.

Context

The Iris Ohyama SMT-PL1 smart plug (https://www.irisohyama.co.jp/smart-plug/) appears to be a Broadlink SP4M-JP. Normally, it's operated with the vendor's affiliated "Home Link" app. But, using the generic Broadlink app, identifies as SP4M-JP. I used instructions in https://community.home-assistant.io/t/setting-up-a-broadlink-sp4m-us-wifi-smart-plug/260796 to get it setup and unlocked.

Proposed change

Add product ID for compatible smart plug.

Type of change

• [ ] Dependency upgrade
• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] New device
• [X] New product id (the device is already supported with a different id)
• [ ] New feature (which adds functionality to an existing device)
• [ ] Breaking change (fix/feature causing existing functionality to break)
• [ ] Code quality improvements to existing code or addition of tests
• [ ] Documentation

Additional information

• This PR fixes issue: fixes #767
• This PR is related to:
• Link to documentation pull request:

Checklist

• [X] The code change is tested and works locally.
• [X] The code has been formatted using Black.
• [X] The code follows the Zen of Python.
• [X] I am creating the Pull Request against the correct branch.
• [ ] Documentation added/updated.

[felipediel]

Closed with https://github.com/mjg59/python-broadlink/pull/782.