SCHED_TTWU_QUEUE is not longer needed since sparc32 now implements IPI

Signed-off-by: Daniel Hellstrom <daniel@gaisler.com>
Reported-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>