Fix: lab3 on-board problems

kernel/lib/uart.c

@@ -162,6 +162,7 @@ size_t uart_getb_async(uint8_t *bytes, size_t len)
   for (; recvlen < len; ++bytes, ++recvlen) {
     while (!uart_readbuf->size)
       wfe(); // wait for interrupt
+  
     *bytes = ringbuffer_bump(uart_readbuf);
   }