btrfs: don't create integrity bioset for btrfs_bioset

btrfs never uses bio integrity data itself, so don't allocate
the integrity pools for btrfs_bioset.

This patch is a revert of the commit b208c2f7 ("btrfs: Fix crash due
to not allocating integrity data for a set").  The integrity data pool
is not needed, the bio-integrity code now handles allocating the
integrity payload without that.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Tested-by: Nikolay Borisov <nborisov@suse.com>
Tested-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -255,14 +255,8 @@ int __init extent_io_init(void)
 			BIOSET_NEED_BVECS))
 		goto free_buffer_cache;
 
-	if (bioset_integrity_create(&btrfs_bioset, BIO_POOL_SIZE))
-		goto free_bioset;
-
 	return 0;
 
-free_bioset:
-	bioset_exit(&btrfs_bioset);
-
 free_buffer_cache:
 	kmem_cache_destroy(extent_buffer_cache);
 	extent_buffer_cache = NULL;