exit: Move oops specific logic from do_exit into make_task_dead

The beginning of do_exit has become cluttered and difficult to read as
it is filled with checks to handle things that can only happen when
the kernel is operating improperly.

Now that we have a dedicated function for cleaning up a task when the
kernel is operating improperly move the checks there.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

kernel/futex/core.c

@@ -1044,7 +1044,7 @@ static void futex_cleanup(struct task_struct *tsk)
  * actually finished the futex cleanup. The worst case for this is that the
  * waiter runs through the wait loop until the state becomes visible.
  *
- * This is called from the recursive fault handling path in do_exit().
+ * This is called from the recursive fault handling path in make_task_dead().
  *
  * This is best effort. Either the futex exit code has run already or
  * not. If the OWNER_DIED bit has been set on the futex then the waiter can