[IB] Add idr_destroy() calls on module unload

Add idr_destroy() calls to the module_exit() functions of the four IB
driver modules that use idrs, so we don't leak idr_layer_cache objects
when these modules are unloaded.

Signed-off-by: Roland Dreier <rolandd@cisco.com>
diff --git a/drivers/infiniband/core/ucm.c b/drivers/infiniband/core/ucm.c
index d0f0b0a..5a6ba40 100644
--- a/drivers/infiniband/core/ucm.c
+++ b/drivers/infiniband/core/ucm.c
@@ -1320,6 +1320,7 @@
 	class_destroy(ib_ucm_class);
 	cdev_del(&ib_ucm_cdev);
 	unregister_chrdev_region(IB_UCM_DEV, 1);
+	idr_destroy(&ctx_id_table);
 }
 
 module_init(ib_ucm_init);