lib: mmutest: Add x86(64) support (kernel only) am: 977b0d8d0d

Original change: https://android-review.googlesource.com/c/trusty/lk/trusty/+/2795817

Change-Id: Id736e16198a5b44856a9e8bfc86c9ee073ae5f49
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>