Change in coreboot[master]: soc/intel/skylake: add soc implementation for ETR address API

[Michael Niewöhner (Code Review)]

Michael Niewöhner has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/36569 )

Change subject: soc/intel/skylake: add soc implementation for ETR address API
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Uploaded patch set 3: Patch Set 2 was rebased.