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/isdn/capi/capi.c b/drivers/isdn/capi/capi.c
index 8a35029..19e005e 100644
--- a/drivers/isdn/capi/capi.c
+++ b/drivers/isdn/capi/capi.c
@@ -1302,11 +1302,12 @@
 #endif
 }
 
-static void capinc_tty_break_ctl(struct tty_struct *tty, int state)
+static int capinc_tty_break_ctl(struct tty_struct *tty, int state)
 {
 #ifdef _DEBUG_TTYFUNCS
 	printk(KERN_DEBUG "capinc_tty_break_ctl(%d)\n", state);
 #endif
+	return 0;
 }
 
 static void capinc_tty_flush_buffer(struct tty_struct *tty)