sh,sh-sci: Use NO_POLL_CHAR in the SCIF polled console code

The sci_poll_get_char() needs to return immediately if there is no
input from the chip to process, and must return a value of
NO_POLL_CHAR.

This allows kgdboc to process multiple polled devices while kgdb is
active.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
Acked-by: NPaul Mundt <lethal@linux-sh.org>

drivers/serial/sh-sci.c

@@ -151,7 +151,11 @@ static int sci_poll_get_char(struct uart_port *port)
 			handle_error(port);
 			continue;
 		}
-	} while (!(status & SCxSR_RDxF(port)));
+		break;
+	} while (1);
+
+	if (!(status & SCxSR_RDxF(port)))
+		return NO_POLL_CHAR;
 
 	c = sci_in(port, SCxRDR);