locking, task_struct: Reduce size on TRACE_IRQFLAGS and 64bit

Reorder task_struct field for TRACE_IRQFLAGS to remove padding
on 64-bit.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4B135F50.8070302@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>