drm/ttm: also export ttm_bo_vm_fault v2

That is needed by at least a cleanup in radeon.

v2: also export ttm_bo_vm_access

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/339353/