Change in coreboot[master]: x86: Add function to modify CR3 register

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Change subject: x86: Add function to modify CR3 register
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Patch Set 3: Verified+1

Build Successful

https://qa.coreboot.org/job/coreboot-gerrit/69370/ : SUCCESS

https://qa.coreboot.org/job/coreboot-checkpatch/23693/ : SUCCESS