ANDROID: KVM: iommu: Restrict access KVM_IOMMU_DOMAIN_IDMAP_ID

KVM_IOMMU_DOMAIN_IDMAP_ID should only mirror the host stage-2,
without interaction with pv interface.

Bug: 277989609
Bug: 278749606
Bug: 424546803
Signed-off-by: Mostafa Saleh <smostafa@google.com>
(cherry picked from https://android-review.googlesource.com/q/commit:1a45ce72b0cfc24e01d278723754ecdb23de2c15)
Merged-In: I6d9800c1a12c9f4dbfbb51c22f589614424aabaa
Change-Id: I6d9800c1a12c9f4dbfbb51c22f589614424aabaa