TTY: mn10300-serial, fix build breakage

By the recent `switch flipping' patches we introduced a build failure
in the driver:
mn10300-serial.c:527:19: error: 'port' redeclared as different kind of symbol

I did not notice because I did not even find a compiler for that new
architecture. Hopefully everything is all right now as I cannot test
it.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/mn10300/kernel/mn10300-serial.c

@@ -524,7 +524,7 @@ static int mask_test_and_clear(volatile u8 *ptr, u8 mask)
 static void mn10300_serial_receive_interrupt(struct mn10300_serial_port *port)
 {
 	struct uart_icount *icount = &port->uart.icount;
-	struct tty_port *port = &port->uart.state->port;
+	struct tty_port *tport = &port->uart.state->port;
 	unsigned ix;
 	int count;
 	u8 st, ch, push, status, overrun;
@@ -534,10 +534,10 @@ static void mn10300_serial_receive_interrupt(struct mn10300_serial_port *port)
 	push = 0;
 
 	count = CIRC_CNT(port->rx_inp, port->rx_outp, MNSC_BUFFER_SIZE);
-	count = tty_buffer_request_room(port, count);
+	count = tty_buffer_request_room(tport, count);
 	if (count == 0) {
-		if (!port->low_latency)
-			tty_flip_buffer_push(port);
+		if (!tport->low_latency)
+			tty_flip_buffer_push(tport);
 		return;
 	}
 
@@ -545,8 +545,8 @@ static void mn10300_serial_receive_interrupt(struct mn10300_serial_port *port)
 	/* pull chars out of the hat */
 	ix = ACCESS_ONCE(port->rx_outp);
 	if (CIRC_CNT(port->rx_inp, ix, MNSC_BUFFER_SIZE) == 0) {
-		if (push && !port->low_latency)
-			tty_flip_buffer_push(port);
+		if (push && !tport->low_latency)
+			tty_flip_buffer_push(tport);
 		return;
 	}
 
@@ -666,19 +666,19 @@ static void mn10300_serial_receive_interrupt(struct mn10300_serial_port *port)
 		else
 			flag = TTY_NORMAL;
 
-		tty_insert_flip_char(port, ch, flag);
+		tty_insert_flip_char(tport, ch, flag);
 	}
 
 	/* overrun is special, since it's reported immediately, and doesn't
 	 * affect the current character
 	 */
 	if (overrun)
-		tty_insert_flip_char(port, 0, TTY_OVERRUN);
+		tty_insert_flip_char(tport, 0, TTY_OVERRUN);
 
 	count--;
 	if (count <= 0) {
-		if (!port->low_latency)
-			tty_flip_buffer_push(port);
+		if (!tport->low_latency)
+			tty_flip_buffer_push(tport);
 		return;
 	}