KVM: selftests: move Hyper-V MSR definitions to hyperv.h

These defines can be shared by multiple tests, move them to a dedicated
header.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210521095204.2161214-29-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>