tty: fix chars_in_buffers

This function does not have an error return and returning an error is
instead interpreted as having a lot of pending bytes.

Reported by Jeff Harris who provided a list of some of the remaining
offenders.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/usb/serial/ti_usb_3410_5052.c b/drivers/usb/serial/ti_usb_3410_5052.c
index 14971a9..3bc609f 100644
--- a/drivers/usb/serial/ti_usb_3410_5052.c
+++ b/drivers/usb/serial/ti_usb_3410_5052.c
@@ -727,7 +727,7 @@
 	dbg("%s - port %d", __func__, port->number);
 
 	if (tport == NULL)
-		return -ENODEV;
+		return 0;
 
 	spin_lock_irqsave(&tport->tp_lock, flags);
 	room = ti_buf_space_avail(tport->tp_write_buf);
@@ -748,7 +748,7 @@
 	dbg("%s - port %d", __func__, port->number);
 
 	if (tport == NULL)
-		return -ENODEV;
+		return 0;
 
 	spin_lock_irqsave(&tport->tp_lock, flags);
 	chars = ti_buf_data_avail(tport->tp_write_buf);