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/char/moxa.c

@@ -1280,6 +1280,7 @@ static int moxa_chars_in_buffer(struct tty_struct *tty)
 	 */
 	if (ch == NULL)
 		return 0;
+	lock_kernel();
 	chars = MoxaPortTxQueue(ch);
 	if (chars) {
 		/*
@@ -1289,6 +1290,7 @@ static int moxa_chars_in_buffer(struct tty_struct *tty)
 		if (!(ch->statusflags & EMPTYWAIT))
 			moxa_setup_empty_event(tty);
 	}
+	unlock_kernel();
 	return chars;
 }