Mark the module as VNDK or VNDK-SP in Android.bp

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

For a VNDK module, the 'vndk' tag has 'enabled: true'.
It will be installed system/lib(64)/vndk as a vendor variant.

For a VNDK-SP module, the 'vndk' tag has
'support_system_process: true' as well as 'enabled: true'.
It will be installed system/lib(64)/vndk-sp as a vendor variant.

Bug: 63866913
Test: build and boot with BOARD_VNDK_VERSION=current
Merged-In: Iee7f2e14fea4635a64c4e5c5bb50f5d7e2691682
Change-Id: Iee7f2e14fea4635a64c4e5c5bb50f5d7e2691682
(cherry picked from commit 439bfbb7d0)

media/libstagefright/foundation/Android.bp

@@ -1,7 +1,9 @@
 cc_library_shared {
     name: "libstagefright_foundation",
     vendor_available: true,
-
+    vndk: {
+        enabled: true,
+    },
     include_dirs: [
         "frameworks/av/include",
         "frameworks/native/include",