Add mbedtls to manifest

Bug: 20752406
Test: repo sync
Change-Id: I7cc85f817812c3f2a6e8f2a804720db18d6dd878
diff --git a/default.xml b/default.xml
index cb353dd..4fce0e3 100644
--- a/default.xml
+++ b/default.xml
@@ -358,6 +358,7 @@
   <project path="external/lzma" name="platform/external/lzma" groups="pdk" />
   <project path="external/marisa-trie" name="platform/external/marisa-trie" groups="pdk" />
   <project path="external/markdown" name="platform/external/markdown" groups="pdk" />
+  <project path="external/mbedtls" name="platform/external/mbedtls" groups="pdk" />
   <project path="external/mdnsresponder" name="platform/external/mdnsresponder" groups="pdk" />
   <project path="external/mesa3d" name="platform/external/mesa3d" groups="pdk-cw-fs,pdk-fs" />
   <project path="external/mime-support" name="platform/external/mime-support" groups="pdk" />