Revert "IB/cm: Mark stale CM id's whenever the mad agent was unregistered"

Revert "IB/cm: Mark stale CM id's whenever the mad agent was unregistered"

This reverts commit 9db0ff53cb9b43ed75bacd42a89c1a0ab048b2b0, which wasn't
a full fix and still causes to the following panic:

panic @ time 1605623870.843, thread 0xfffffeb63b552000: vm_fault_lookup: fault on nofault entry, addr: 0xfffffe811a94e000
    time = 1605623870
    cpuid = 9, TSC = 0xb7937acc1b6
    Panic occurred in module kernel loaded at 0xffffffff80200000:Stack: --------------------------------------------------
    kernel:vm_fault+0x19da
    kernel:vm_fault_trap+0x6e
    kernel:trap_pfault+0x1f1
    kernel:trap+0x31e
    kernel:cm_destroy_id+0x38c
    kernel:rdma_destroy_id+0x127
    kernel:sdp_shutdown_task+0x3ae
    kernel:taskqueue_run_locked+0x10b
    kernel:taskqueue_thread_loop+0x87
    kernel:fork_exit+0x83

Link: https://lore.kernel.org/r/4346449a7cdacc7a4eedc89cb1b42d8434ec9814.1622629024.git.leonro@nvidia.com
Signed-off-by: Mark Zhang <markzhang@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>