Update the PLIC based on the [riscv-plic-spec](https://github.com/riscv/riscv-plic-spec) in the PR: - Support customized PLIC hardID and privilege mode configuration - Backward compatable with the n_contexts parameter, will generate the config like {0,M}, {0,S}, {1,M} ... Change-Id: Ibff736827edb7c97921e01fa27f503574a27a562