KVM: nVMX: Report 2MB EPT pages as supported

As long as the hardware provides us 2MB EPT pages, we can also expose
them to the guest because our shadow EPT code already supports this
feature.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>