block: Allow 0ms latency, increase the read speed
Change a timer compare from after to after-equals, thus allowing
0 timeout and making deadline and sio schedulers FIFO.

Signed-off-by: xiaobing tu <xiaobing.tu@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Based off @tuxiaobing's original patch for deadline