[RISCV] Add the CSR names from Smrnmi. (#83370)

Specification is here
https://github.com/riscv/riscv-isa-manual/blob/main/src/rnmi.adoc

CSRs numbers defined here
https://github.com/riscv/riscv-isa-manual/blob/main/src/priv-csrs.adoc