x86: corruption check: run the corruption checks from a work queue

Impact: change the implementation of the debug feature

the periodic corruption checks are better off run from a work queue; there's
nothing time critical about them and this way the amount of
interrupt-context work is reduced.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>