Export dnode symbols

External consumers such as Lustre require access to the dnode
interfaces in order to correctly manipulate dnodes.

Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Olaf Faaland <faaland1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue openzfs#8994
Closes openzfs#9027

module/zfs/dnode.c

@@ -2483,3 +2483,13 @@ dnode_next_offset(dnode_t *dn, int flags, uint64_t *offset,
 
 	return (error);
 }
+
+#if defined(_KERNEL)
+EXPORT_SYMBOL(dnode_hold);
+EXPORT_SYMBOL(dnode_rele);
+EXPORT_SYMBOL(dnode_set_nlevels);
+EXPORT_SYMBOL(dnode_set_blksz);
+EXPORT_SYMBOL(dnode_free_range);
+EXPORT_SYMBOL(dnode_evict_dbufs);
+EXPORT_SYMBOL(dnode_evict_bonus);
+#endif