Add assembler for riscv64, part 4. am: 5d567e508e am: 013a957d48 am: 7bfc7858cc

Original change: https://android-review.googlesource.com/c/platform/art/+/2598686

Change-Id: I6f2d674622613f11c4b368d6da05c6f1c46df5e0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>