drm/amdgpu: fix amdgpu_vm_clear_freed v2

Use amdgpu_vm_bo_update_mapping() instead of amdgpu_vm_bo_split_mapping() here.

We don't want any flags set in the cleared areas and splitting
shouldn't be necessary.

v2: fix typo in commit message

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org