Make the UART not constantly flush output

src/basic_uart.rs

@@ -64,7 +64,6 @@ impl BasicUart {
         while let Some(byte) = bufs.tx.pop_front() {
             print!("{}", byte as char);
         }
-        stdout().flush().unwrap();
 
         let mut buffer = [0u8; 1];
         if let Ok(n) = stdin().read(&mut buffer) {