update SDK

Neutree · Neutree · commit 2a4ae48f711e · 2019-03-28T17:31:00.000+08:00
diff --git a/cores/arduino/kendryte-standalone-sdk b/cores/arduino/kendryte-standalone-sdk
@@ -1 +1 @@
-Subproject commit 174349202037a760e1865210b15a0703566e8064
+Subproject commit 7440800a8e6c6ee760e8f3a761fe366fbc3972cd
