blk-iocost: Simplify ioc_rqos_done()

Leave out the superfluous "& REQ_OP_MASK" code. The definition of req_op()
shows that that code is superfluous:

 #define req_op(req) ((req)->cmd_flags & REQ_OP_MASK)

Compile-tested only.

Cc: Tejun Heo <tj@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220615225549.1054905-2-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-iocost.c

@@ -2769,7 +2769,7 @@ static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq)
 	if (!ioc->enabled || !rq->alloc_time_ns || !rq->start_time_ns)
 		return;
 
-	switch (req_op(rq) & REQ_OP_MASK) {
+	switch (req_op(rq)) {
 	case REQ_OP_READ:
 		pidx = QOS_RLAT;
 		rw = READ;