KVM: x86: always fill in vcpu->arch.hv_clock

KVM: x86: always fill in vcpu->arch.hv_clock

We will use it in the next patches for KVM_GET_CLOCK and as a basis for the
contents of the Hyper-V TSC page.  Get the values from the Linux
timekeeper even if kvmclock is not enabled.

Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 0d6dd2ff8206dc1da3428d5b1611f6304d481dab)

Orabug: 27146591

Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>