Fixed kbd (buffer flush)

src/io/serial/serial.c

@@ -54,6 +54,7 @@ static int is_transmit_empty()
 // Serial kernel putchar
 void skputc(char c)
 {
+    // TODO: Spinlock here (serial access)
     while (!is_transmit_empty()); // wait for free spot
     outb(PORT, c);
 }