blk-mq: remove REQ_ATOM_STARTED

After the recent updates to use generation number and state based
synchronization, we can easily replace REQ_ATOM_STARTED usages by
adding an extra state to distinguish completed but not yet freed
state.

Add MQ_RQ_COMPLETE and replace REQ_ATOM_STARTED usages with
blk_mq_rq_state() tests.  REQ_ATOM_STARTED no longer has any users
left and is removed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 6b2d616..8591a54 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -34,6 +34,7 @@
 enum mq_rq_state {
 	MQ_RQ_IDLE		= 0,
 	MQ_RQ_IN_FLIGHT		= 1,
+	MQ_RQ_COMPLETE		= 2,
 
 	MQ_RQ_STATE_BITS	= 2,
 	MQ_RQ_STATE_MASK	= (1 << MQ_RQ_STATE_BITS) - 1,