update csr to draft-20200326-af69f79 (#39)
update csr to draft-20200326-af69f79 (#39)

about two parts
   1. hypervisor related
   2. missing high part for rv32

Signed-off-by: Chih-Min Chao <13dd11b28ffb6e9b0c779cd7f9c69b6c1d4e73ca@sifive.com>
riscv/riscv-opcodes,riscv/riscv-opcodes