KVM: x86: prevent MWAIT in guest with buggy MONITOR

The bug prevents MWAIT from waking up after a write to the monitored
cache line.
KVM might emulate a CPU model that shouldn't have the bug, so the guest
would not employ a workaround and possibly miss wakeups.
Better to avoid the situation.

Reviewed-by: Alexander Graf <agraf@suse.de>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>