xilinx_uartlite: suppress "cannot receive message"

This message is not an error condition, its just informing the user that
the device is corking the uart traffic to not drop characters.

Reported-by: Jason Wu <huanyu@xilinx.com>
Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
diff --git a/hw/xilinx_uartlite.c b/hw/xilinx_uartlite.c
index d20fc41..f890f23 100644
--- a/hw/xilinx_uartlite.c
+++ b/hw/xilinx_uartlite.c
@@ -182,12 +182,8 @@
 static int uart_can_rx(void *opaque)
 {
     struct xlx_uartlite *s = opaque;
-    int r;
 
-    r = s->rx_fifo_len < sizeof(s->rx_fifo);
-    if (!r)
-        printf("cannot receive!\n");
-    return r;
+    return s->rx_fifo_len < sizeof(s->rx_fifo);
 }
 
 static void uart_event(void *opaque, int event)