xor_writer: use 64bit for partition size am: 80e4391ccc am: 0c92112363

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/3349246

Change-Id: Ic39d2b22a77c10c59804080cbd86657f16d8f2de
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>