KVM: x86: Do runtime CPUID update before updating vcpu->arch.cpuid_entries

kvm_update_cpuid_runtime() mangles CPUID data coming from userspace
VMM after updating 'vcpu->arch.cpuid_entries', this makes it
impossible to compare an update with what was previously
supplied. Introduce __kvm_update_cpuid_runtime() version which can be
used to tweak the input before it goes to 'vcpu->arch.cpuid_entries'
so the upcoming update check can compare tweaked data.

No functional change intended.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20220117150542.2176196-2-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>