pm: schedule sysrq poweroff on boot cpu

schedule sysrq poweroff on boot cpu.

sysrq poweroff needs to disable nonboot cpus, and we need to run this on boot
cpu to avoid any recursion.  http://bugzilla.kernel.org/show_bug.cgi?id=10897

[kosaki.motohiro@jp.fujitsu.com: build fix]
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Tested-by: Rus <harbour@sfinx.od.ua>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>