Add product_available to libbinder_tokio_rs

Vendors already can use libbinder_tokio_rs on /vendor. This change makes
them available to /product as well, just like libbinder_rs.

More about product partitions:
https://source.android.com/docs/core/architecture/partitions/product-partitions

Bug: 336989719
Test: mm
Change-Id: I6c388c27b4fe6b7b1ff317bbfab424958fb6a6a9
diff --git a/libs/binder/rust/Android.bp b/libs/binder/rust/Android.bp
index ef556d7..725744c 100644
--- a/libs/binder/rust/Android.bp
+++ b/libs/binder/rust/Android.bp
@@ -59,6 +59,7 @@
     ],
     host_supported: true,
     vendor_available: true,
+    product_available: true,
     target: {
         darwin: {
             enabled: false,