slab: Rename list3/l3 to node

The list3 or l3 pointers are pointing to per node structures. Reflect
that in the names of variables used.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

diff --cc mm/slab.c
Simple merge

diff --cc mm/slab.h
Simple merge