lightnvm: fix incorrect nr_free_blocks stat

BugLink: http://bugs.launchpad.net/bugs/1531539

When initing bad block list in gennvm_block_bb, once we move bad block
from free_list to bb_list, we should maintain both stat info
nr_free_blocks and nr_bad_blocks. So this patch fixes to add missing
operation related to nr_free_blocks.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>
(cherry picked from commit bdded155)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/lightnvm/gennvm.c

@@ -89,6 +89,7 @@ static int gennvm_block_bb(struct ppa_addr ppa, int nr_blocks, u8 *blks,
 
 		list_move_tail(&blk->list, &lun->bb_list);
 		lun->vlun.nr_bad_blocks++;
+		lun->vlun.nr_free_blocks--;
 	}
 
 	return 0;