Document loopback UART registers
Document loopback UART registers

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jbush001/NyuziProcessor,jbush001/NyuziProcessor,FulcronZ/NyuziProcessor,FulcronZ/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor,FulcronZ/NyuziProcessor,FulcronZ/NyuziProcessor,jbush001/NyuziProcessor,jbush001/NyuziProcessor