freertos: release the generic version source code

freertos runs on the second core (small one) of the CPU

freertos/cvitek/driver/uart/include/uart.h

@@ -0,0 +1,14 @@
+#ifndef _UART_H_
+#define _UART_H_
+#ifdef __riscv
+#include <stdint.h>
+#else
+#include "linux/types.h"
+#endif
+void uart_init(void);
+int uart_getc(void);
+int uart_tstc(void);
+uint8_t uart_putc(uint8_t ch);
+void uart_puts(char *str);
+int uart_put_buff(char *buf);
+#endif