drm/ttm: add NUMA node id to the pool

This allows backing ttm_tt structure with pages from different NUMA
pools.

Tested-by: Graham Sider <graham.sider@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>