libkeystore-wifi-hidl: Updated to vendor_available:true

Updated libkeystore-wifi-hidl from 'vendor: true' to 'vendor_available: true'

Test: Build libkeystore-wifi-hidl
Bug: 187130384

Change-Id: Ifba05b57248f52ac33e297acd5d0b7811e3524ee
diff --git a/keystore/Android.bp b/keystore/Android.bp
index 0ab5198..b59bacc 100644
--- a/keystore/Android.bp
+++ b/keystore/Android.bp
@@ -102,5 +102,5 @@
 
     export_include_dirs: ["include"],
 
-    vendor: true,
+    vendor_available: true,
 }