KVM: x86: Remove unused "vcpu" of kvm_scale_tsc()

The "struct kvm_vcpu *vcpu" parameter of kvm_scale_tsc() is not used,
so remove it. No functional change intended.

Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
Message-Id: <20220125095909.38122-18-cloudliang@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>