Add aconfig flags for rust keystore2

Test: m keystore2
Change-Id: I0bdd3d34a4e78500b266b8aac321ff1e2903dffb
diff --git a/keystore2/aconfig/flags.aconfig b/keystore2/aconfig/flags.aconfig
new file mode 100644
index 0000000..04bbddc
--- /dev/null
+++ b/keystore2/aconfig/flags.aconfig
@@ -0,0 +1,8 @@
+package: "android.security.keystore2"
+
+flag {
+  name: "wal_db_journalmode"
+  namespace: "hardware_backed_security"
+  description: "This flag controls changing journalmode to wal"
+  bug: "191777960"
+}