Make apex_available of nn hidl interfaces explicit in Android.bp

These are available to com.android.neuralnetworks via the baseline
apexAvailable map in build/soong/apex/apex.go. This CL makes this
explicit in Android.bp

Test: m nothing #passes
Bug: 281077552
Change-Id: I9f08db0dba6b155c6f25393a5d4baf6de27110da
diff --git a/neuralnetworks/1.1/Android.bp b/neuralnetworks/1.1/Android.bp
index 772e5e6..b93c80c 100644
--- a/neuralnetworks/1.1/Android.bp
+++ b/neuralnetworks/1.1/Android.bp
@@ -21,4 +21,8 @@
         "android.hidl.base@1.0",
     ],
     gen_java: false,
+    apex_available: [
+        "//apex_available:platform",
+        "com.android.neuralnetworks",
+    ],
 }