target-i386/kvm: Hyper-V SynIC MSR's support

This patch does Hyper-V Synthetic interrupt
controller(Hyper-V SynIC) MSR's support and
migration. Hyper-V SynIC is enabled by cpu's
'hv-synic' option.

This patch does not allow cpu creation if
'hv-synic' option specified but kernel
doesn't support Hyper-V SynIC.

Changes v3:
* removed 'msr_hv_synic_version' migration because
it's value always the same
* moved SynIC msr's initialization into kvm_arch_init_vcpu

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Richard Henderson <rth@twiddle.net>
CC: Eduardo Habkost <ehabkost@redhat.com>
CC: "Andreas Färber" <afaerber@suse.de>
CC: Marcelo Tosatti <mtosatti@redhat.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: kvm@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>