drm/amdgpu: Add ioctl to get all gem handles for a process

drm/amdgpu: Add ioctl to get all gem handles for a process

Add new ioctl DRM_IOCTL_AMDGPU_GEM_LIST_HANDLES.

This ioctl returns a list of bos with their handles, sizes,
and flags and domains.

This ioctl is meant to be used during CRIU checkpoint and
provide information needed to reconstruct the bos
in CRIU restore.

Userspace for this and the next change can be found at
https://github.com/checkpoint-restore/criu/pull/2613

Signed-off-by: David Francis <David.Francis@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>