Reduce the NUMA text size of mm/slab.o a little on x86 by using a local
variable to store the result of numa_node_id().

    text    data     bss     dec     hex filename
   16858    2584      16   19458    4c02 mm/slab.o (before)
   16804    2584      16   19404    4bcc mm/slab.o (after)

[akpm@osdl.org: use better names]
[pbadari@us.ibm.com: fix that]
Cc: Christoph Lameter <christoph@lameter.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>