IB/cm: Convert to using idr_alloc_cyclic()

Commit 3e6628c4b347 ("idr: introduce idr_alloc_cyclic()") adds a new
idr_alloc_cyclic() routine and converts several of these users to it.
This is just a missed one - add it.

Signed-off-by: Zhao Hongjiang <zhaohongjiang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Roland Dreier <roland@purestorage.com>