Fully qualify @attr reference to android.R field am: 6815c5cd36

Original change: https://android-review.googlesource.com/c/platform/packages/apps/Car/SystemUI/+/3296933

Change-Id: I3a1433bd092bd979d30a7bc01182c1e980ac88fb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>