backing-dev: Kill set but not used var in bdi_debug_stats_show()

Signed-off-by: NGustavo F. Padovan <padovan@profusion.mobi>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

mm/backing-dev.c

@@ -63,10 +63,10 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
 	unsigned long background_thresh;
 	unsigned long dirty_thresh;
 	unsigned long bdi_thresh;
-	unsigned long nr_dirty, nr_io, nr_more_io, nr_wb;
+	unsigned long nr_dirty, nr_io, nr_more_io;
 	struct inode *inode;
 
-	nr_wb = nr_dirty = nr_io = nr_more_io = 0;
+	nr_dirty = nr_io = nr_more_io = 0;
 	spin_lock(&inode_wb_list_lock);
 	list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
 		nr_dirty++;