bcache: remove can_attach_cache()

After removing the embedded struct cache_sb from struct cache_set, cache
set will directly reference the in-memory super block of struct cache.
It is unnecessary to compare block_size, bucket_size and nr_in_set from
the identical in-memory super block in can_attach_cache().

This is a preparation patch for latter removing cache_set->sb from
struct cache_set.

Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/bcache/super.c

@@ -2127,13 +2127,6 @@ err:
 	return -EIO;
 }
 
-static bool can_attach_cache(struct cache *ca, struct cache_set *c)
-{
-	return ca->sb.block_size	== c->sb.block_size &&
-		ca->sb.bucket_size	== c->sb.bucket_size &&
-		ca->sb.nr_in_set	== c->sb.nr_in_set;
-}
-
 static const char *register_cache_set(struct cache *ca)
 {
 	char buf[12];
@@ -2145,9 +2138,6 @@ static const char *register_cache_set(struct cache *ca)
 			if (c->cache)
 				return "duplicate cache set member";
 
-			if (!can_attach_cache(ca, c))
-				return "cache sb does not match set";
-
 			if (!CACHE_SYNC(&ca->sb))
 				SET_CACHE_SYNC(&c->sb, false);