RDMA/rtrs: Add missing deinit() call

In the Linux kernel, the following vulnerability has been resolved:

RDMA/rtrs: Add missing deinit() call

A warning is triggered when repeatedly connecting and disconnecting the

rnbd:

list_add corruption. prev->next should be next (ffff88800b13e480), but was ffff88801ecd1338. (prev=ffff88801ecd1340).

WARNING: CPU: 1 PID: 36562 at lib/list_debug.c:32 __list_add_valid_or_report+0x7f/0xa0

Workqueue: ib_cm cm_work_handler [ib_cm]

RIP: 0010:__list_add_valid_or_report+0x7f/0xa0

? __list_add_valid_or_report+0x7f/0xa0

ib_register_event_handler+0x65/0x93 [ib_core]

rtrs_srv_ib_dev_init+0x29/0x30 [rtrs_server]

rtrs_ib_dev_find_or_add+0x124/0x1d0 [rtrs_core]

__alloc_path+0x46c/0x680 [rtrs_server]

? rtrs_rdma_connect+0xa6/0x2d0 [rtrs_server]

? rcu_is_watching+0xd/0x40

? __mutex_lock+0x312/0xcf0

? get_or_create_srv+0xad/0x310 [rtrs_server]

? rtrs_rdma_connect+0xa6/0x2d0 [rtrs_server]

rtrs_rdma_connect+0x23c/0x2d0 [rtrs_server]

? __lock_release+0x1b1/0x2d0

cma_cm_event_handler+0x4a/0x1a0 [rdma_cm]

cma_ib_req_handler+0x3a0/0x7e0 [rdma_cm]

cm_process_work+0x28/0x1a0 [ib_cm]

? _raw_spin_unlock_irq+0x2f/0x50

cm_req_handler+0x618/0xa60 [ib_cm]

cm_work_handler+0x71/0x520 [ib_cm]

Commit 667db86bcbe8 ("RDMA/rtrs: Register ib event handler") introduced a

new element .deinit but never used it at all. Fix it by invoking the

`deinit()` to appropriately unregister the IB event handler.