Review LGPL-2.1 license headers

[Adrian-Stanea]

Introduction

This PR standardizes the license headers and fixes version mismatches, ensuring all files use LGPL v2.1 instead of v2 or v3.

To be discussed

1. These files are currently under the more restrictive ADI-BSD license. They should be reviewed to either replace them with alternatives under a more permissive license or to ensure proper mention of their license in the documentation or project files.
   • [x] include/libm2k/tools/i2c.hpp
   • [x] include/libm2k/tools/spi.hpp
   • [x] include/libm2k/tools/uart.hpp
2. Consider adding a CI check to ensure that certain files contain the appropriate license headers. The CI check should fail if any files do not follow the established license guidelines.

Note

The following files and directories have been omitted from the reviewed files:

Directories:

• .git*
• build
• CI
• img
• results
• wingetopt

Files:

• *.png
• *.rst
• .gitignore
• 53-adi-m2k-usb.rules
• AssemblyInfo.cs.in
• azure-pipelines.yml
• Doxyfile.in
• Doxyfile_API.in
• README*
• key.snk
• libm2k-sharp.dll.config.cmakein
• libm2k-sharp.pc.cmakein
• libm2k.i
• libm2k.pc.cmakein
• libm2kData.xml
• requirements.txt
• version.hpp.cmakein

[Adrian-Stanea]

later edit: We should not modify the license headers in files from deps/wingetopt

Removed license header from cmake file from tools/deps/wingetopt

[Adrian-Stanea]

Replaced ADI-BSD license