Add an internal flag NVGPU_MEM_FLAG_FOREIGN_SGT to specify that the sgt member of an nvgpu_mem must not be freed when the nvgpu_mem is freed. Bug 200145225 Change-Id: I044fb91a5f9d148f38fb0cbf63d0cdfd64a070ce Signed-off-by: Konsta Holtta <kholtta@nvidia.com> Reviewed-on: https://git-master.nvidia.com/r/1819801 Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com> Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>