compat: backport idr_alloc() usage

This backports a patch series send by Tejun Heo:
https://lkml.org/lkml/2013/2/2/159

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
compat: backport drop of node parameter from iterators

This patch backports the following commit in mainline linux kernel:

  commit 0bbacca7c3911451cea923b0ad6389d58e3d9ce9
  Author: Sasha Levin <sasha.levin@oracle.com>
  Date:   Thu Feb 7 12:32:18 2013 +1100

      hlist: drop the node parameter from iterators

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>