tty: rework break handling

Some hardware needs to do break handling itself and may have partial
support only. Make break_ctl return an error code. Add a tty driver flag
so you can indicate driver hardware side break support.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/char/amiserial.c b/drivers/char/amiserial.c
index 37457e5..3530ff4 100644
--- a/drivers/char/amiserial.c
+++ b/drivers/char/amiserial.c
@@ -1248,7 +1248,7 @@
 /*
  * rs_break() --- routine which turns the break handling on or off
  */
-static void rs_break(struct tty_struct *tty, int break_state)
+static int rs_break(struct tty_struct *tty, int break_state)
 {
 	struct async_struct * info = (struct async_struct *)tty->driver_data;
 	unsigned long flags;
@@ -1263,6 +1263,7 @@
 	  custom.adkcon = AC_UARTBRK;
 	mb();
 	local_irq_restore(flags);
+	return 0;
 }