mxser: switch to put_char being int

diff -u --new-file --recursive --exclude-from /usr/src/exclude linux.vanilla-2.6.25-rc8-mm2/drivers/char/mxser.c linux-2.6.25-rc8-mm2/drivers/char/mxser.c
@@ -1289,16 +1289,16 @@
 	return total;
 }
 
-static void mxser_put_char(struct tty_struct *tty, unsigned char ch)
+static int mxser_put_char(struct tty_struct *tty, unsigned char ch)
 {
 	struct mxser_port *info = tty->driver_data;
 	unsigned long flags;
 
 	if (!info->xmit_buf)
-		return;
+		return 0;
 
 	if (info->xmit_cnt >= SERIAL_XMIT_SIZE - 1)
-		return;
+		return 0;
 
 	spin_lock_irqsave(&info->slock, flags);
 	info->xmit_buf[info->xmit_head++] = ch;

@@ -1316,6 +1316,7 @@
 			spin_unlock_irqrestore(&info->slock, flags);
 		}
 	}
+	return 1;
 }