cstyle fixes
dsl_dataset_set_fsid_guid should use ZFS_SPACE_CHECK_RESERVED
dsl_dataset_set_fsid_guid _check and _sync func declared static,
removed from dsl_dataset.h
rewrite unique_valid
6333 ZFS should let the user specify or modify the fsid_guid of a dataset

@@ -337,10 +337,12 @@
     zprop_source_t source, uint64_t value, dmu_tx_t *tx);
 void dsl_dataset_zapify(dsl_dataset_t *ds, dmu_tx_t *tx);
 boolean_t dsl_dataset_is_zapified(dsl_dataset_t *ds);
 boolean_t dsl_dataset_has_resume_receive_state(dsl_dataset_t *ds);
 int dsl_dataset_rollback(const char *fsname, void *owner, nvlist_t *result);
+int dsl_dataset_set_fsid_guid(const char *ddname, zprop_source_t source,
+    uint64_t fsid_guid);
 
 void dsl_dataset_deactivate_feature(uint64_t dsobj,
     spa_feature_t f, dmu_tx_t *tx);
 
 #ifdef ZFS_DEBUG