drm/amdkfd: Copy HW exception data to user event

Fixes issue where user events of type KFD_EVENT_TYPE_HW_EXCEPTION do not
have valid data

Signed-off-by: David Yat Sin <David.YatSin@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>