x86: merge init_task_32/64.c

Merge init_task_32/64.c.
Move 64bit per cpu data orig_ist to setup64.c.

[ mingo: fixed checkpatch trivialities. ]

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>