The redo label needs #ifdeffery. Fixes the following problem introduced by
commit 8a5ec0ba ("Lockless (and preemptless) fastpaths for slub"):

  mm/slub.c: In function 'slab_free':
  mm/slub.c:2124: warning: label 'redo' defined but not used
Reported-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NChristoph Lameter <cl@linux.com>
Signed-off-by: NPekka Enberg <penberg@kernel.org>