ZFS: whitelist zstd and encryption in the loader

Please note that neither zstd nor encryption is
supported by the loader at this instant. This
change makes it safe to use those features in
one's root pool, but not in one's root dataset.

stand/libsa/zfs/zfsimpl.c

@@ -127,6 +127,8 @@ static const char *features_for_read[] = {
 	"com.delphix:device_removal",
 	"com.delphix:obsolete_counts",
 	"com.intel:allocation_classes",
+	"org.freebsd:zstd_compress",
+	"com.datto:encryption",
 	NULL
 };