selftests: kvm: add tsc_scaling_sync to .gitignore

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2074832



commit 0c8b6641
Author: Like Xu <like.xu.linux@gmail.com>
Date:   Wed Apr 6 14:37:13 2022 +0800

    selftests: kvm: add tsc_scaling_sync to .gitignore

    The tsc_scaling_sync's binary should be present in the .gitignore
    file for the git to ignore it.

Signed-off-by: Like Xu <likexu@tencent.com>
    Message-Id: <20220406063715.55625-3-likexu@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>