hyperv: ensure SINTx msrs are reset properly

Initially SINTx msrs should be in "masked" state.  To ensure that
happens on *every* reset, move setting their values to
kvm_arch_vcpu_reset.

Signed-off-by: Roman Kagan <rkagan@virtuozzo.com>
Message-Id: <20171122181418.14180-3-rkagan@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>