rtc: mc146818: Reduce spinlock section in mc146818_set_time()

stable inclusion
from stable-v5.10.159
commit db44a9443e586077594808a09820dfe6f408b8b6
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7NTXH

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=db44a9443e586077594808a09820dfe6f408b8b6



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[ Upstream commit dcf257e9 ]

No need to hold the lock and disable interrupts for doing math.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201206220541.709243630@linutronix.de


Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>