io_uring: deduplicate failing task_work_add

mainline inclusion
from mainline-5.12-rc1
commit eab30c4d
category: bugfix
bugzilla: 182869 https://gitee.com/openeuler/kernel/issues/I4DDEL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=eab30c4d20dc761d463445e5130421863ff81505



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When io_req_task_work_add() fails, the request will be cancelled by
enqueueing via task_works of io-wq. Extract a function for that.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Conflicts:
	fs/io_uring.c
	[ 355fb9e2("io_uring: remove 'twa_signal_ok' deadlock
	  work-around") is not applied. ]

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>

Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>