legal: Add SPDX header for MSLA licensed code

[rzr]

For the record reusability has been improved a bit:

Files with license information: 272 / 307

The following files have no licensing information:

• common/spinel.h
• tools/tbu/api.yaml

Origin: https://github.com/SiliconLabs/wisun-br-linux/pulls?q=author%3Arzr

[jerome-pouiller]

I believe we need to add LICENSES/LicenseRef-MSLA.txt

[rzr]

or move 4015bac44c57f062fdb5e08a5b2795a7 LICENSE to it

I have been asking if there is a stable plain text version of it

[MathisMARION]

I believe LICENSE-Apache-2.0 and LICENSE-BSD-3-Clause should be moved to the new LICENSES/ folder.

Finally, is LICENSE still needed?

[rzr]

yes this will be my next PR :)

[MathisMARION]

Applied to our private development branch. This should be released with v2.1.4, thank you for your contribution!

[rzr]

For the record this PR is automatically closed on rebase (push force)

cc: @MathisMARION

[rzr]

For the record, reuse report (more changes to come)

SUMMARY

• Bad licenses: 0
• Deprecated licenses: 0
• Licenses without file extension: 0
• Missing licenses: GPL-2.0, Apache-2.0
• Unused licenses: 0
• Used licenses: GPL-2.0, Apache-2.0, LicenseRef-MSLA
• Read errors: 0
• files with copyright information: 272 / 307
• files with license information: 272 / 307