RDMA/ib_srp: Fix a deadlock

stable inclusion
from stable-v5.10.103
commit 99eb8d694174c777558dc902d575d1997d5ca650
bugzilla: https://gitee.com/openeuler/kernel/issues/I56NE7

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=99eb8d694174c777558dc902d575d1997d5ca650

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[ Upstream commit 081bdc9f ]

Remove the flush_workqueue(system_long_wq) call since flushing
system_long_wq is deadlock-prone and since that call is redundant with a
preceding cancel_work_sync()

Link: https://lore.kernel.org/r/20220215210511.28303-3-bvanassche@acm.org


Fixes: ef6c49d8 ("IB/srp: Eliminate state SRP_TARGET_DEAD")
Reported-by:  <syzbot+831661966588c802aae9@syzkaller.appspotmail.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>