[PATCH v5] Add CRIU support for amdgpu dmabuf

[David Francis]

(previous patches were incorrectly called v3 but were actually the 4th version)

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

In this v5, the drm interfaces have been changed from creating buffer objects
with specified gem handles to changing the gem handle of an existing buffer
object. This new ioctl (AMDGPU_GEM_CHANGE_HANDLE) is in drm_gem.c

In the accompanying CRIU patch set, the sockets used by CRIU to exchange dmabuf
fds between restoring processes have been refactored to be created within the
amdgpu plugin itself.