manifest: add vendor/interfaces

Change-Id: Id35f1fba219330b468464e8009d095dd013a159d

omni-default.xml

@@ -14,6 +14,7 @@
   <project path="android" name="android" remote="omnirom" revision="android-9.0" />
 
   <project path="vendor/omni" name="android_vendor_omni" remote="omnirom" revision="android-9.0" />
+  <project path="vendor/interfaces" name="android_vendor_interfaces" remote="omnirom" revision="android-9.0" />
 
   <project path="external/bash" name="android_external_bash" remote="omnirom" revision="android-9.0" />
   <project path="external/exfat" name="android_external_exfat" remote="omnirom" revision="android-8.1" />