ipmi/watchdog: replace atomic_add() and atomic_sub()

mainline inclusion
from v5.11-rc1
commit a01a89b1
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5DVR9
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a01a89b1db1066a6af23ae08b9a0c345b7966f0b



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atomic_inc() and atomic_dec() looks better

Signed-off-by: Yejune Deng <yejune.deng@gmail.com>
Message-Id: <1605511807-7135-1-git-send-email-yejune.deng@gmail.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Li JinLin <lijinlin3@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>