Drivers: hv: restore TSC page cleanup before kexec

We need to cleanup the TSC page before doing kexec/kdump or the new kernel
may crash if it tries to use it.

Fixes: 63ed4e0c

 ("Drivers: hv: vmbus: Consolidate all Hyper-V specific clocksource code")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>