md: remove legacy 1s delay in md_notify_reboot

md: remove legacy 1s delay in md_notify_reboot

During system shutdown, the md driver registered notifier function
(md_notify_reboot) currently imposes a hardcoded one-second delay.

This delay was introduced approximately 23 years ago and was likely
necessary for the hardware generation of that time. Proposing this
patch to make sure there are no known devices that need this delay.

Link: https://lore.kernel.org/linux-raid/20251121191422.2758555-1-tarunsahu@google.com
Signed-off-by: Tarun Sahu <tarunsahu@google.com>
Reviewed-by: Yu Kuai<yukuai@fnnas.com>
Signed-off-by: Yu Kuai <yukuai@fnnas.com>