md: Revert "md: Fix overflow in is_mddev_idle"

This reverts commit 3f9f2312.

Using 64bit for 'sync_io' is unnecessary from the gendisk side. This
overflow will not cause any functional impact, except for a UBSAN
warning. Solving this overflow requires introducing additional
calculations and checks which are not necessary. So just keep using
32bit for 'sync_io'.

Signed-off-by: Li Nan <linan122@huawei.com>
Link: https://lore.kernel.org/r/20240507023103.781816-1-linan666@huaweicloud.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>