riscv: Add indirect stringification to csr_xxx ops

riscv: Add indirect stringification to csr_xxx ops

With current csr_xxx ops, we cannot pass a macro to parameter
'csr', hence we need add another level to allow the parameter
to be a macro itself, aka indirect stringification.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Anup Patel <anup@brainfault.org>