Adding Tn48m

[toganlabs]

TN48m is newly supported

mion-docs

Summary

• Description: brief description of the bug that was fixed or the enhancement that was added
• Affected hardware: ALL -or- list specific switches
• Issue: #?

Build and test

• Build command: e.g. mc_build.sh ...
• Smoke tested on: e.g. stordis bf2556x-1t
• all other steps taken to validate the pull request

Checklist

• All relevant issues have been updated
• Reviewers have been added and a maintainer has been assigned
• A Label, Project and Milestone have all been added
• The relevant documentation/wiki/README have been updated and complies with the NGL Style and Communication Guide
• Git commits comply with the NGL Git Workflow and have DCO signoff
• Yocto code complies with the OpenEmbedded Style Guide