Mark libbinder and libdumpstateutil as VNDK in Android.bp

As a VNDK module, Android.bp must have 'vndk' tag as well as
'vendor_available: true'.

The 'vndk' tag for VNDK module is formated as below:
vndk: {
    enabled: true,
},

VNDK modules will be installed both in system/lib(64) as normal and
in system/lib(64)/vndk as a vendor variant.

Bug: 63866913
Test: build and boot with BOARD_VNDK_VERSION=current
Change-Id: Ib1d9469ad0aead4cbec7c2548438d44608f36819
diff --git a/libs/binder/Android.bp b/libs/binder/Android.bp
index 748105c..09fd0cb 100644
--- a/libs/binder/Android.bp
+++ b/libs/binder/Android.bp
@@ -33,6 +33,9 @@
 
     // for vndbinder
     vendor_available: true,
+    vndk: {
+        enabled: true,
+    },
 
     srcs: [
         "AppOpsManager.cpp",