Add third_party/dtc project

Change-Id: I99a74157438c80fece58f8da4dfd6221307aecbe
diff --git a/default.xml b/default.xml
index f84daa6..62d8df0 100644
--- a/default.xml
+++ b/default.xml
@@ -26,6 +26,7 @@
 
   <!-- Shallow clones of third-party code. -->
   <project path="prebuilts" name="hafnium/prebuilts" clone-depth="1" />
+  <project path="third_party/dtc" name="hafnium/third_party/dtc" clone-depth="1" />
   <project path="third_party/googletest" name="hafnium/third_party/googletest" clone-depth="1" />
   <project path="third_party/linux" name="hafnium/third_party/linux" clone-depth="1" />