Mark libion vendor_available.

libion belongs to vndk-cap. Mark it vendor_available to enable vndk
abi stability checks on it.

Details: https://android-review.googlesource.com/368372

Test: mm -j64

Bug: 38244611

Merged-In: I195145af90433c29ce9e408197e8d7183cb960bc
Change-Id: I8ac290d435b7c4dc5e669bfccb4562495ce92516
(cherry picked from commit 2e31a8c4f99454cc6ac5292c952fef7166614e5f)
diff --git a/libion/Android.bp b/libion/Android.bp
index da98111..6f267e4 100644
--- a/libion/Android.bp
+++ b/libion/Android.bp
@@ -1,6 +1,7 @@
 
 cc_library {
     name: "libion",
+		vendor_available: true,
     srcs: ["ion.c"],
     shared_libs: ["liblog"],
     local_include_dirs: [