x86, tsc: Fix a preemption leak in restore_sched_clock_state()

Doh, a real life genuine preemption leak..

This caused a suspend failure.

Reported-bisected-and-tested-by-the-invaluable: Jeff Chua <jeff.chua.linux@gmail.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Nico Schottelius <nico-linux-20100709@schottelius.org>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Florian Pritz <flo@xssn.at>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: <stable@kernel.org> # Greg, please apply after: cd7240c0 ("x86, tsc, sched: Recompute cyc2ns_offset's during resume from")
sleep states
LKML-Reference: <1284150773.402.122.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>