KVM: x86: SVM: add module param to control LBR virtualization

This is useful for debug and also makes it consistent with
the rest of the SVM optional features.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210914154825.104886-9-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>