x86/vtd: fix IOMMU share PT destruction path

x86/vtd: fix IOMMU share PT destruction path

Commit 2916951c1 ("mm / iommu: include need_iommu() test in
iommu_use_hap_pt()") included need_iommu() in iommu_use_hap_pt and
91d4eca7add ("mm / iommu: split need_iommu() into has_iommu_pt() and
need_iommu_pt_sync()") made things finer grain by spliting need_iommu
into three states.

The destruction path can't use iommu_use_hap_pt because at the point
platform op is called, IOMMU is either already switched to or has
always been in disabled state, and the shared PT test would always be
false.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>