x86, NUMA: Rename setup_node_bootmem() to setup_node_data()

After using memblock to replace bootmem, that function only sets up
node_data now.

Change the name to reflect what it actually does.

tj: Minor adjustment to the patch description.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>