Update FreeBSD tunables

Remove some obsolete legacy compat, rename some misnamed, and add some
missing tunables for FreeBSD.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #10203

include/os/linux/kernel/linux/mod_compat.h

@@ -54,6 +54,7 @@ enum scope_prefix_types {
 	zfs_dbuf,
 	zfs_dbuf_cache,
 	zfs_deadman,
+	zfs_dedup,
 	zfs_l2arc,
 	zfs_livelist,
 	zfs_livelist_condense,
@@ -67,13 +68,13 @@ enum scope_prefix_types {
 	zfs_send,
 	zfs_spa,
 	zfs_trim,
+	zfs_txg,
 	zfs_vdev,
 	zfs_vdev_cache,
 	zfs_vdev_mirror,
 	zfs_zevent,
 	zfs_zio,
-	zfs_zil,
-	spa
+	zfs_zil
 };
 
 /*