Convert framework-protos to Android.bp

See build/soong/README.md for more information.

Test: m checkbuild
Change-Id: Id7992ff0cc5d631b64c1fa8e82e8a130ea508236
diff --git a/Android.bp b/Android.bp
index b9f000b..7d75f62 100644
--- a/Android.bp
+++ b/Android.bp
@@ -71,6 +71,7 @@
     "core/*",
     "libs/*",
     "media/*",
+    "proto",
     "tools/*",
     "native/android",
     "native/graphics/jni",