block: fix the problem of io_ticks becoming smaller

On the IO submission path, blk_account_io_start() may interrupt
the system interruption. When the interruption returns, the value
of part->stamp may have been updated by other cores, so the time
value collected before the interruption may be less than part->
stamp. So when this happens, we should do nothing to make io_ticks
more accurate? For kernels less than 5.0, this may cause io_ticks
to become smaller, which in turn may cause abnormal ioutil values.

Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/1625521646-1069-1-git-send-email-brookxu.cn@gmail.com


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