tty_port: Fix return on interrupted use

Whoops.. fortunately not many people use this yet.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/char/tty_port.c b/drivers/char/tty_port.c
index 4e862a7..9769b11 100644
--- a/drivers/char/tty_port.c
+++ b/drivers/char/tty_port.c
@@ -267,7 +267,7 @@
 	if (retval == 0)
 		port->flags |= ASYNC_NORMAL_ACTIVE;
 	spin_unlock_irqrestore(&port->lock, flags);
-	return 0;
+	return retval;
 	
 }
 EXPORT_SYMBOL(tty_port_block_til_ready);