bcache: remove redundant variables i and n

Variables i and n are being assigned but are never used. They are
redundant and can be removed.
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NColy Li <colyli@suse.de>
Addresses-Coverity: ("Unused value")
Signed-off-by: NJens Axboe <axboe@kernel.dk>

drivers/md/bcache/btree.c

@@ -1907,10 +1907,8 @@ static int bch_btree_check_thread(void *arg)
 	struct btree_iter iter;
 	struct bkey *k, *p;
 	int cur_idx, prev_idx, skip_nr;
-	int i, n;
 
 	k = p = NULL;
-	i = n = 0;
 	cur_idx = prev_idx = 0;
 	ret = 0;