tick/sched: Optimize tick_do_update_jiffies64() further

mainline inclusion
from mainline-5.11-rc1
commit 7a35bf2a
category: feature
feature: Deep isolation
bugzilla: https://gitee.com/openeuler/kernel/issues/I4N00D
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7a35bf2a6a871cd0252cd371d741e7d070b53af9



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Now that it's clear that there is always one tick to account, simplify the
calculations some more.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.565663056@linutronix.de


Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Reviewed-by: Chao Liu <liuchao173@huawei.com>
Reviewed-by: Chen Hui <judy.chenhui@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>