target/riscv: Add CSR name in the CSR function table

target/riscv: Add CSR name in the CSR function table

In preparation to generate the CSR register list for GDB stub
dynamically, let's add the CSR name in the CSR function table.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 1610427124-49887-3-git-send-email-bmeng.cn@gmail.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>