Convert to the much saner new idr interface.  Error return values from
recover_idr_add() mix -1 and -errno.  The conversion doesn't change
that but it looks iffy.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>