serial: sh-sci: mask SCTFDR/RFDR according to fifosize

Current mask 0xff to SCTFDR/RFDR damages SCIFB, because the
registers on SCIFB have 9-bit data (0 to 256).

This patch changes the mask according to port->fifosize.
Though I'm not sure if the mask is really needed (I don't know if
there are variants which have non-zero upper bits), it is safer.
Signed-off-by: Takashi Yoshii <takashi.yoshii.zj@renesas.com>
Signed-off-by: Shinya Kuribayashi <shinya.kuribayashi.px@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sh-sci.c

@@ -485,7 +485,7 @@ static int sci_txfill(struct uart_port *port)
 
 	reg = sci_getreg(port, SCTFDR);
 	if (reg->size)
-		return serial_port_in(port, SCTFDR) & 0xff;
+		return serial_port_in(port, SCTFDR) & ((port->fifosize << 1) - 1);
 
 	reg = sci_getreg(port, SCFDR);
 	if (reg->size)
@@ -505,7 +505,7 @@ static int sci_rxfill(struct uart_port *port)
 
 	reg = sci_getreg(port, SCRFDR);
 	if (reg->size)
-		return serial_port_in(port, SCRFDR) & 0xff;
+		return serial_port_in(port, SCRFDR) & ((port->fifosize << 1) - 1);
 
 	reg = sci_getreg(port, SCFDR);
 	if (reg->size)