Change name of overlay subdir property to sku.

Also move the SKU subdirectories directly under /vendor/overlay.

Bug: 31692079
Change-Id: I68c712b13918cc99629534580ee4f77d9e5b3823
diff --git a/include/androidfw/AssetManager.h b/include/androidfw/AssetManager.h
index 0b22802..099d82e 100644
--- a/include/androidfw/AssetManager.h
+++ b/include/androidfw/AssetManager.h
@@ -73,12 +73,11 @@
     static const char* IDMAP_BIN;
     static const char* OVERLAY_DIR;
     /*
-     * If OVERLAY_SUBDIR_PROPERTY is set, search for runtime resource overlay
-     * APKs in OVERLAY_SUBDIR/<value of OVERLAY_SUBDIR_PROPERTY>/ rather than in
+     * If OVERLAY_SKU_DIR_PROPERTY is set, search for runtime resource overlay
+     * APKs in OVERLAY_DIR/<value of OVERLAY_SKU_DIR_PROPERTY> rather than in
      * OVERLAY_DIR.
      */
-    static const char* OVERLAY_SUBDIR;
-    static const char* OVERLAY_SUBDIR_PROPERTY;
+    static const char* OVERLAY_SKU_DIR_PROPERTY;
     static const char* TARGET_PACKAGE_NAME;
     static const char* TARGET_APK_PATH;
     static const char* IDMAP_DIR;