IB/core: Fix unused variable warning
IB/core: Fix unused variable warning

Fix the below "make W=1" build warning:

    drivers/infiniband/core/iwcm.c: In function ‘destroy_cm_id’:
    drivers/infiniband/core/iwcm.c:330: warning: variable ‘ret’ set but not used

Signed-off-by: Or Gerlitz <de1b678a59344538ef9f2ddb34a5f9486544e2f9@mellanox.com>
Signed-off-by: Roland Dreier <0d270388f2f92757a5de0f4bd891d3b392c44c4f@purestorage.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs