drm/amdgpu: handle PTE MTYPE in amdgpu_vm_bo_split_mapping

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Xie <AlexBin.Xie@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>