Fix tethering build after ag/21363239

This commit fixes tethering apex build errors after ag/21363239:
- Remove unsupported field in Android.bp: "frozen: false"
- Add owner field to Android.bp to bypass compilation check of using
  unfrozen AIDL interfaces: owner: "google"

Bug: b/205762647
Test: build and install tethering apex:
      banchan com.google.android.tethering module_x86_64
      UNBUNDLED_BUILD_SDKS_FROM_SOURCE=true m apps_only dist
      adb install out/dist/com.google.android.tethering.apex
Change-Id: Iea77f2117834c1317b3ab16f71881a6b2e299474