libs: libfdt: Fix Fdt::header() using bad pointer am: 68980bee75

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/modules/Virtualization/+/23107375

Change-Id: I66ed668ca124c73e21fb728314d37f0ba743f5aa
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>