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/stallion.c

@@ -875,6 +875,7 @@ static void stl_waituntilsent(struct tty_struct *tty, int timeout)
 		timeout = HZ;
 	tend = jiffies + timeout;
 
+	lock_kernel();
 	while (stl_datastate(portp)) {
 		if (signal_pending(current))
 			break;
@@ -882,6 +883,7 @@ static void stl_waituntilsent(struct tty_struct *tty, int timeout)
 		if (time_after_eq(jiffies, tend))
 			break;
 	}
+	unlock_kernel();
 }
 
 /*****************************************************************************/