btrfs: constify fs_info argument for the reclaim items calculation helpers

Now that btrfs_calc_insert_metadata_size() can take a const fs_info
argument, make the fs_info argument of calc_reclaim_items_nr() and of
calc_delayed_refs_nr() const as well.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
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

@@ -537,7 +537,7 @@ void btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
 	up_read(&info->groups_sem);
 }
 
-static inline u64 calc_reclaim_items_nr(struct btrfs_fs_info *fs_info,
+static inline u64 calc_reclaim_items_nr(const struct btrfs_fs_info *fs_info,
 					u64 to_reclaim)
 {
 	u64 bytes;
@@ -550,7 +550,7 @@ static inline u64 calc_reclaim_items_nr(struct btrfs_fs_info *fs_info,
 	return nr;
 }
 
-static inline u64 calc_delayed_refs_nr(struct btrfs_fs_info *fs_info,
+static inline u64 calc_delayed_refs_nr(const struct btrfs_fs_info *fs_info,
 				       u64 to_reclaim)
 {
 	u64 bytes;