Allow rkpd mainline module to link rkp aidl bits

Test: Build
Change-Id: Ide8b4ec4b8994368d035f79054818542aba306e5
diff --git a/security/rkp/aidl/Android.bp b/security/rkp/aidl/Android.bp
index 4c479f4..5285477 100644
--- a/security/rkp/aidl/Android.bp
+++ b/security/rkp/aidl/Android.bp
@@ -21,6 +21,10 @@
     backend: {
         java: {
             min_sdk_version: "33",
+            apex_available: [
+                "//apex_available:platform",
+                "com.android.rkpd",
+            ],
         },
         rust: {
             enabled: true,