add silk for IOS

[linphone] / oRTP

diff --git a/oRTP b/oRTP
index d1ca9b6c5fbcaafa59299dc1a5f790bb92dc4e6e..7606207905bd3dc661e68576097adce471916697 160000 (submodule)
--- a/oRTP
+++ b/oRTP
@@ -1 +1 @@
-Subproject commit d1ca9b6c5fbcaafa59299dc1a5f790bb92dc4e6e
+Subproject commit 7606207905bd3dc661e68576097adce471916697