tty: switch tty_port::xmit_* to u8

Both xmit_buf and xmit_fifo of struct tty_port should be u8. To conform
to characters in the rest of the tty layer.
Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20231206073712.17776-4-jirislaby@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_port.c

@@ -247,7 +247,7 @@ int tty_port_alloc_xmit_buf(struct tty_port *port)
 	/* We may sleep in get_zeroed_page() */
 	mutex_lock(&port->buf_mutex);
 	if (port->xmit_buf == NULL) {
-		port->xmit_buf = (unsigned char *)get_zeroed_page(GFP_KERNEL);
+		port->xmit_buf = (u8 *)get_zeroed_page(GFP_KERNEL);
 		if (port->xmit_buf)
 			kfifo_init(&port->xmit_fifo, port->xmit_buf, PAGE_SIZE);
 	}

include/linux/tty_port.h

@@ -114,8 +114,8 @@ struct tty_port {
 	unsigned char		console:1;
 	struct mutex		mutex;
 	struct mutex		buf_mutex;
-	unsigned char		*xmit_buf;
-	DECLARE_KFIFO_PTR(xmit_fifo, unsigned char);
+	u8			*xmit_buf;
+	DECLARE_KFIFO_PTR(xmit_fifo, u8);
 	unsigned int		close_delay;
 	unsigned int		closing_wait;
 	int			drain_delay;