Mark libprotobuf-cpp-lite as double_loadable

libprotobuf-cpp-lite is a VNDK lib and also used by LLNDK(libmediandk)
which means this lib can be double-loaded.
(deps: libmediandk -> libmedia_jni -> libmediadrm -> libprotobuf-cpp-lite)

Bug: 121280180
Test: m -j
Change-Id: I2b221f3064cab169c76b94f1a40722f57925fb96
diff --git a/Android.bp b/Android.bp
index 63d602a..0fdeb42 100644
--- a/Android.bp
+++ b/Android.bp
@@ -110,6 +110,7 @@
     vndk: {
         enabled: true,
     },
+    double_loadable: true,
     defaults: ["libprotobuf-cpp-lite-defaults"],
 
     cflags: ["-DGOOGLE_PROTOBUF_NO_RTTI"],