iommu: fix KASAN use-after-free in iommu_insert_resv_region

iommu: fix KASAN use-after-free in iommu_insert_resv_region

In case the new region gets merged into another one, the nr list node is
freed.  Checking its type while completing the merge algorithm leads to
a use-after-free.  Use new->type instead.

Fixes: 4dbd258ff63e ("iommu: Revisit iommu_insert_resv_region() implementation")
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reported-by: Qian Cai <cai@lca.pw>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Cc: Stable <stable@vger.kernel.org> #v5.3+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>