tty/serial: lay the foundations for the next set of reworks

- Stop drivers calling their own flush method indirectly, it obfuscates code
  and it will change soon anyway

- A few more lock_kernel paths temporarily needed in some driver internal
  waiting code

- Remove private put_char method that does a write call for one char - we
  have that anyway

- Most but not yet all of the termios copy under lock fixing (some has other
  dependencies to follow)

- Note a few locking bugs in drivers found in the process

- Kill remaining [ab]users of TIOCG/SSOFTCAR in the driver, these must go to
  fix the termios locking

Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/isdn/i4l/isdn_tty.c

@@ -1708,9 +1708,7 @@ isdn_tty_close(struct tty_struct *tty, struct file *filp)
 	}
 	dev->modempoll--;
 	isdn_tty_shutdown(info);
-	
-	if (tty->driver->flush_buffer)
-		tty->driver->flush_buffer(tty);
+	isdn_tty_flush_buffer(tty);
 	tty_ldisc_flush(tty);
 	info->tty = NULL;
 	info->ncarrier = 0;