KVM: VMX: Don't enable EPT A/D feature if EPT feature is disabled

We can observe eptad kvm_intel module parameter is still Y
even if ept is disabled which is weird. This patch will
not enable EPT A/D feature if EPT feature is disabled.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>