[PATCH v8] Add CRIU support for amdgpu dmabuf

[David Francis]

This patch series adds support for CRIU checkpointing of processes that
share memory with the amdgpu dmabuf interface.

This v8 incorporates the vm mapping rework, which it depends on.
(https://lore.kernel.org/amd-gfx/880855c5-dede-4497-8ca1-916bd0dbd08a@amd.com/T/#u)

Accompanying CRIU changes:
https://github.com/checkpoint-restore/criu/pull/2613