KVM: x86: Rename kvm_update_cpuid() to kvm_vcpu_after_set_cpuid()

Now there is no updating CPUID bits behavior in kvm_update_cpuid(),
rename it to kvm_vcpu_after_set_cpuid().

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Message-Id: <20200709043426.92712-4-xiaoyao.li@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>