Add tinycrypt 0.2.8

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/ext/tinycrypt/VERSION b/ext/tinycrypt/VERSION
index 53a75d6..a45be46 100644
--- a/ext/tinycrypt/VERSION
+++ b/ext/tinycrypt/VERSION
@@ -1 +1 @@
-0.2.6
+0.2.8