get rid of compile time warning: "warning: ‘android_ids’ defined but not used"

Change-Id: If365bd88f735d425f37d61bcd5a6903f99f6a454
diff --git a/include/private/android_filesystem_config.h b/include/private/android_filesystem_config.h
index 1dbe171..97b873a 100644
--- a/include/private/android_filesystem_config.h
+++ b/include/private/android_filesystem_config.h
@@ -76,7 +76,7 @@
     unsigned aid;
 };
 
-static struct android_id_info android_ids[] = {
+static const struct android_id_info android_ids[] = {
     { "root",      AID_ROOT, },
     { "system",    AID_SYSTEM, },
     { "radio",     AID_RADIO, },