Add assembler for riscv64, part 4.

Implement fences, LR/SC and atomic operations.

Test: m  test-art-host-gtest
Bug: 283082089
Signed-off-by: Lifang Xia <lifang_xia@linux.alibaba.com>
Signed-off-by: Wendong Wang <wangwd@xcvmbyte.com>
Signed-off-by: Cao Xia <caoxia@eswincomputing.com>
Change-Id: If10463d33071db577c4cc775ad3700c1746e093d
4 files changed