Block: use round_jiffies_up()

This patch (as1159b) changes the timeout routines in the block core to
use round_jiffies_up().  There's no point in rounding the timer
deadline down, since if it expires too early we will have to restart
it.

The patch also removes some unnecessary tests when a request is
removed from the queue's timer list.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>