btrfs: cleanup init for list in free-space-cache

o removed an unecessary INIT_LIST_HEAD after LIST_HEAD

o merge a declare & INIT_LIST_HEAD pair into one LIST_HEAD
Signed-off-by: NGui Hecheng <guihc.fnst@cn.fujitsu.com>
Reviewed-by: NDavid Sterba <dsterba@suse.cz>
Signed-off-by: NChris Mason <clm@fb.com>

fs/btrfs/free-space-cache.c

@@ -651,15 +651,13 @@ static int __load_free_space_cache(struct btrfs_root *root, struct inode *inode,
 	struct io_ctl io_ctl;
 	struct btrfs_key key;
 	struct btrfs_free_space *e, *n;
-	struct list_head bitmaps;
+	LIST_HEAD(bitmaps);
 	u64 num_entries;
 	u64 num_bitmaps;
 	u64 generation;
 	u8 type;
 	int ret = 0;
 
-	INIT_LIST_HEAD(&bitmaps);
-
 	/* Nothing in the space cache, goodbye */
 	if (!i_size_read(inode))
 		return 0;
@@ -2905,7 +2903,6 @@ int btrfs_find_space_cluster(struct btrfs_root *root,
 	trace_btrfs_find_cluster(block_group, offset, bytes, empty_size,
 				 min_bytes);
 
-	INIT_LIST_HEAD(&bitmaps);
 	ret = setup_cluster_no_bitmap(block_group, cluster, &bitmaps, offset,
 				      bytes + empty_size,
 				      cont1_bytes, min_bytes);