drm/amdgpu: save vm fault information for amdkfd

amdgpu save the vm fault related information for KFD usage and keep the
copy until KFD read it.

Signed-off-by: shaoyun liu <shaoyun.liu@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>