x86: kvm: style: Simplify bool comparison

Fix the following coccicheck warning:
./arch/x86/kvm/x86.c:8012:5-48: WARNING: Comparison to bool

Signed-off-by: YANG LI <abaci-bugfix@linux.alibaba.com>
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Message-Id: <1610357578-66081-1-git-send-email-abaci-bugfix@linux.alibaba.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>