Impact: fix time warps under vmware

Similar to the check for TSC going backwards in the TSC clocksource,
we also need this check for VMI clocksource.
Signed-off-by: NAlok N Kataria <akataria@vmware.com>
Cc: Zachary Amsden <zach@vmware.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Cc: stable@kernel.org