Change in coreboot[master]: timer: Add helper function stopwatch_wait_until_expired

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Change subject: timer: Add helper function stopwatch_wait_until_expired
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Patch Set 2: Verified+1

Build Successful

https://qa.coreboot.org/job/coreboot-gerrit/60707/ : SUCCESS

https://qa.coreboot.org/job/coreboot-checkpatch/15909/ : SUCCESS