btrfs: fix slab cache flags for free space tree bitmap

The free space tree bitmap slab cache is created with SLAB_RED_ZONE but
that's a debugging flag and not always enabled. Also the other slabs are
created with at least SLAB_MEM_SPREAD that we want as well to average
the memory placement cost.
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Fixes: 3acd4850 ("btrfs: fix allocation of free space cache v1 bitmap pages")
CC: stable@vger.kernel.org # 5.4+
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -9005,7 +9005,7 @@ int __init btrfs_init_cachep(void)
 
 	btrfs_free_space_bitmap_cachep = kmem_cache_create("btrfs_free_space_bitmap",
 							PAGE_SIZE, PAGE_SIZE,
-							SLAB_RED_ZONE, NULL);
+							SLAB_MEM_SPREAD, NULL);
 	if (!btrfs_free_space_bitmap_cachep)
 		goto fail;