serial: mux: Convert to uart_console_device instead of open-coded

The implementation of mux_console_device() is very similar to
uart_console_device(). Setting .data field in mux_console then we can
convert to use uart_console_device().
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/mux.c

@@ -412,19 +412,14 @@ static int mux_console_setup(struct console *co, char *options)
         return 0;
 }
 
-struct tty_driver *mux_console_device(struct console *co, int *index)
-{
-        *index = co->index;
-	return mux_driver.tty_driver;
-}
-
 static struct console mux_console = {
 	.name =		"ttyB",
 	.write =	mux_console_write,
-	.device =	mux_console_device,
+	.device =	uart_console_device,
 	.setup =	mux_console_setup,
 	.flags =	CON_ENABLED | CON_PRINTBUFFER,
 	.index =	0,
+	.data =		&mux_driver,
 };
 
 #define MUX_CONSOLE	&mux_console