Imported more library files

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Libs/protocol/openthread/platform-abstraction/efr32/uart.h

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+#ifndef _UART_H
+#define _UART_H
+
+#include <stdbool.h>
+
+/**
+ * The size of the receive buffer
+ *
+ */
+#define RECEIVE_BUFFER_SIZE 128
+
+/**
+ * This function initializes the UART interface.
+ *
+ */
+void efr32UartInit(void);
+
+/**
+ * This function performs UART processing.
+ *
+ */
+void efr32UartProcess(void);
+
+/**
+ * This function informs the caller whether UART
+ * operations are ready to process
+ *
+ * @return true if RX or TX data is ready to process.
+ */
+bool efr32UartIsDataReady(void);
+
+#endif // _UART_H