omni: Update to ap4a release configs

Change-Id: I61a01cfbe35676364a19e6d9e7de193b43ea5868
diff --git a/release/release_configs/ap4a.textproto b/release/release_configs/ap4a.textproto
new file mode 100644
index 0000000..6eee39c
--- /dev/null
+++ b/release/release_configs/ap4a.textproto
@@ -0,0 +1,3 @@
+name: "ap4a"
+prior_stages: "trunk"
+aconfig_value_sets: "aconfig_value_set-omnirom-ap4a"