char/serial: Fix emptyness handling

The commit 88c1ee73
char/serial: Fix emptyness check

Still causes extra NULL byte(s) to be sent.

So if the fifo is empty, do not send an extra NULL byte.
Reviewed-by: NPeter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: NDon Slutz <dslutz@verizon.com>
Message-id: 1395160174-16006-1-git-send-email-dslutz@verizon.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/char/serial.c

@@ -225,8 +225,10 @@ static gboolean serial_xmit(GIOChannel *chan, GIOCondition cond, void *opaque)
 
     if (s->tsr_retry <= 0) {
         if (s->fcr & UART_FCR_FE) {
-            s->tsr = fifo8_is_empty(&s->xmit_fifo) ?
-                        0 : fifo8_pop(&s->xmit_fifo);
+            if (fifo8_is_empty(&s->xmit_fifo)) {
+                return FALSE;
+            }
+            s->tsr = fifo8_pop(&s->xmit_fifo);
             if (!s->xmit_fifo.num) {
                 s->lsr |= UART_LSR_THRE;
             }