KVM: TDX: WARN if mirror SPTE doesn't have full RWX when creating S-EPT mapping

KVM: TDX: WARN if mirror SPTE doesn't have full RWX when creating S-EPT mapping

Pass in the mirror_spte to kvm_x86_ops.set_external_spte() to provide
symmetry with .remove_external_spte(), and assert in TDX that the mirror
SPTE is shadow-present with full RWX permissions (the TDX-Module doesn't
allow the hypervisor to control protections).

Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>
Tested-by: Yan Zhao <yan.y.zhao@intel.com>
Tested-by: Kai Huang <kai.huang@intel.com>
Link: https://patch.msgid.link/20251030200951.3402865-13-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>