x86/NUMA: cleanup

x86/NUMA: cleanup

- drop the only left CONFIG_NUMA conditional (this is always true)
- drop struct node_data's node_id field (being always equal to the
  node_data[] array index used)
- don't open code node_{start,end}_pfn() nor node_spanned_pages()
  except when used as lvalues (those could be converted too, but this
  seems a little awkward)
- no longer open code pfn_to_paddr() in an expression being modified
  anyway
- make dump less verbose by logging actual vs intended node IDs only
  when they don't match

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>