bcache: Remove redundant parameter for cache_alloc()

Cache_sb is not used in cache_alloc, and we have copied
sb info to cache->sb already, remove it.
Reviewed-by: NColy Li <colyli@suse.de>
Signed-off-by: NYijing Wang <wangyijing@huawei.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

drivers/md/bcache/super.c

@@ -1806,7 +1806,7 @@ void bch_cache_release(struct kobject *kobj)
 	module_put(THIS_MODULE);
 }
 
-static int cache_alloc(struct cache_sb *sb, struct cache *ca)
+static int cache_alloc(struct cache *ca)
 {
 	size_t free;
 	struct bucket *b;
@@ -1861,7 +1861,7 @@ static int register_cache(struct cache_sb *sb, struct page *sb_page,
 	if (blk_queue_discard(bdev_get_queue(ca->bdev)))
 		ca->discard = CACHE_DISCARD(&ca->sb);
 
-	ret = cache_alloc(sb, ca);
+	ret = cache_alloc(ca);
 	if (ret != 0)
 		goto err;