Change in coreboot[master]: KGPE-D16 code: Add SPDX license header to all files missing it

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Attention is currently required from: Michał Żygowski.
[e-mail] has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/62115 )

Change subject: KGPE-D16 code: Add SPDX license header to all files missing it
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Patch Set 6:

(1 comment)

Patchset:

PS6: 
The change downgrades some of the license from GPL-2.0-or-later to GPL-2.0-only. It would be great to prefer GPL-2.0-or-later where simple to do so.