Removed list_size struct member from user space list implementation

Removed the list_size struct member as it was only used in a single
assertion, as mentioned in PR openzfs#15478.

Signed-off-by: MigeljanImeri <imerimigel@gmail.com>

lib/libspl/include/sys/list_impl.h

@@ -39,7 +39,6 @@ struct list_node {
 };
 
 struct list {
-	size_t	list_size;
 	size_t	list_offset;
 	struct list_node list_head;
 };

lib/libspl/list.c

@@ -62,10 +62,9 @@ void
 list_create(list_t *list, size_t size, size_t offset)
 {
 	ASSERT(list);
-	ASSERT(size > 0);
-	ASSERT(size >= offset + sizeof (list_node_t));
 
-	list->list_size = size;
+	(void) size;
+
 	list->list_offset = offset;
 	list->list_head.next = list->list_head.prev = &list->list_head;
 }
@@ -194,7 +193,6 @@ list_move_tail(list_t *dst, list_t *src)
 	list_node_t *dstnode = &dst->list_head;
 	list_node_t *srcnode = &src->list_head;
 
-	ASSERT(dst->list_size == src->list_size);
 	ASSERT(dst->list_offset == src->list_offset);
 
 	if (list_empty(src))