Btrfs: remove wait queue from space_info structure

It is not used anymore since commit 957780eb ("Btrfs: introduce
ticketed enospc infrastructure"), so just remove it.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/space-info.c

@@ -58,7 +58,6 @@ static int create_space_info(struct btrfs_fs_info *info, u64 flags)
 	spin_lock_init(&space_info->lock);
 	space_info->flags = flags & BTRFS_BLOCK_GROUP_TYPE_MASK;
 	space_info->force_alloc = CHUNK_ALLOC_NO_FORCE;
-	init_waitqueue_head(&space_info->wait);
 	INIT_LIST_HEAD(&space_info->ro_bgs);
 	INIT_LIST_HEAD(&space_info->tickets);
 	INIT_LIST_HEAD(&space_info->priority_tickets);

fs/btrfs/space-info.h

@@ -63,7 +63,6 @@ struct btrfs_space_info {
 	struct rw_semaphore groups_sem;
 	/* for block groups in our same type */
 	struct list_head block_groups[BTRFS_NR_RAID_TYPES];
-	wait_queue_head_t wait;
 
 	struct kobject kobj;
 	struct kobject *block_group_kobjs[BTRFS_NR_RAID_TYPES];