[coreboot-gerrit] Change in coreboot[master]: src/mainboard: Use SPDX for GPL-2.0-only files

[Angel Pons (Code Review)]

Angel Pons has abandoned this change. ( https://review.coreboot.org/c/coreboot/+/40055 )

Change subject: src/mainboard: Use SPDX for GPL-2.0-only files
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Abandoned

Still way too large, I have split it out