irq_work: Cleanup

mainline inclusion
from mainline-v5.11-rc1
commit 7a9f50a0
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4U05V


CVE: NA

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Get rid of the __call_single_node union and clean up the API a little
to avoid external code relying on the structure layout as much.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: Cheng Jian <cj.chengjian@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>