Change in coreboot[master]: src/include: Add guards on all header files

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Change subject: src/include: Add guards on all header files
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Patch Set 2: Verified+1

Build Successful

https://qa.coreboot.org/job/coreboot-gerrit/57989/ : SUCCESS

https://qa.coreboot.org/job/coreboot-checkpatch/13427/ : SUCCESS