MDEV-12266: Remove fil_space_t::name_hash

The fil_system_t::name_hash was removed already earlier,
in commit 05863142.
The fil_space_t::name_hash was thus made an orphan data field.

storage/innobase/include/fil0fil.h

@@ -146,7 +146,6 @@ struct fil_space_t {
 	Protected by fil_system.mutex and my_atomic_loadlint() and friends. */
 	ulint		n_pending_ios;
 	hash_node_t	hash;	/*!< hash chain node */
-	hash_node_t	name_hash;/*!< hash chain the name_hash table */
 	rw_lock_t	latch;	/*!< latch protecting the file space storage
 				allocation */
 	UT_LIST_NODE_T(fil_space_t) unflushed_spaces;