Change in coreboot[master]: soc/intel/skylake: Add config for enabling LTR for PCIe Root port

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Change subject: soc/intel/skylake: Add config for enabling LTR for PCIe Root port
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Patch Set 1: Verified+1

Build Successful

https://qa.coreboot.org/job/coreboot-checkpatch/15716/ : SUCCESS

https://qa.coreboot.org/job/coreboot-gerrit/60512/ : SUCCESS