License Update

[steven-bellock]

The DMTF has modified its software license guidelines, as detailed in https://www.dmtf.org/sites/default/files/DMTF_Software_Submission_Policy_04-03-2024.pdf, from a BSD 3-Clause license with patent disclaimers and clauses to a straight and unmodified BSD 3-Clause license. As such libspdm and its associated repositories have moved to the unmodified BSD 3-Clause license, and GitHub recognizes the license as such. This should allow for a more straightforward integration of libspdm and its associated repositories into other code bases and remove the need to evaluate the patent disclaimers and clauses.