Update makefiles for hidl_interface.

Bug: 35570956
Test: manual
Change-Id: I7a220b78ee081240e1dc30ef5672ba39e3e98375
diff --git a/Android.bp b/Android.bp
index 7ae00b6..978559a 100644
--- a/Android.bp
+++ b/Android.bp
@@ -2,6 +2,11 @@
     "*"
 ]
 
+hidl_package_root {
+    name: "android.hardware",
+    path: "hardware/interfaces",
+}
+
 cc_defaults {
     name: "hidl_defaults",
     cflags: [