Change in coreboot[master]: rockchip: Correct UART reference clock value

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Change subject: rockchip: Correct UART reference clock value
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Patch Set 2: Verified+1

Build Successful

https://qa.coreboot.org/job/coreboot-gerrit/66938/ : SUCCESS

https://qa.coreboot.org/job/coreboot-checkpatch/21521/ : SUCCESS