lightnvm: fix lun offset calculation for mark blk

The gen_mark_blk_bad function marks the wrong block when a block is on
a different channel. Fix the index calculation, so that it updates the
correct block.
Reported-by: Javier Gonzalez <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/lightnvm/gennvm.c

@@ -542,7 +542,7 @@ static void gen_mark_blk(struct nvm_dev *dev, struct ppa_addr ppa, int type)
 		return;
 	}
 
-	lun = &gn->luns[ppa.g.lun * ppa.g.ch];
+	lun = &gn->luns[(dev->luns_per_chnl * ppa.g.ch) + ppa.g.lun];
 	blk = &lun->vlun.blocks[ppa.g.blk];
 
 	/* will be moved to bb list on put_blk from target */