Change in coreboot[master]: soc/nvidia/tegra210: define missing UART clocks sources

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Change subject: soc/nvidia/tegra210: define missing UART clocks sources
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Patch Set 1: Verified+1

Build Successful

https://qa.coreboot.org/job/coreboot-gerrit/67588/ : SUCCESS

https://qa.coreboot.org/job/coreboot-checkpatch/22106/ : SUCCESS