platform: generic-arm64: Remove reference to HAFNIUM_ARCH am: 5e9696172e

Original change: https://android-review.googlesource.com/c/trusty/lk/trusty/+/3463911

Change-Id: Iaced441a4d78714a846620fbdbe5bbf9df878c0a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>