Add support sign-extension mov instructions for RV64.
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Acked-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/r/20230824095001.3408573-4-pulehui@huaweicloud.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>