bdi: remove unused stuff

Two flags and one bdi_writeback field are no longer used.  Remove
them.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@fb.com>

include/linux/backing-dev.h

@@ -28,12 +28,10 @@ struct dentry;
  * Bits in backing_dev_info.state
  */
 enum bdi_state {
-	BDI_wb_alloc,		/* Default embedded wb allocated */
 	BDI_async_congested,	/* The async (write) queue is getting full */
 	BDI_sync_congested,	/* The sync queue is getting full */
 	BDI_registered,		/* bdi_register() was done */
 	BDI_writeback_running,	/* Writeback is in progress */
-	BDI_unused,		/* Available bits start here */
 };
 
 typedef int (congested_fn)(void *, int);
@@ -50,7 +48,6 @@ enum bdi_stat_item {
 
 struct bdi_writeback {
 	struct backing_dev_info *bdi;	/* our parent bdi */
-	unsigned int nr;
 
 	unsigned long last_old_flush;	/* last old data flush */