Instructions: sync from riscv-opcodes

The current Instructions.scala is not up-to-date with riscv-opcodes

Previous changes on this file seems to be adding new instructions manually,
this can be inferred from
https://github.com/riscv/riscv-opcodes/commit/e2ebbf53340bd856cde5eabfaa6b15831c791478
which changed the name from parse-opcodes to parse_opcodes
thus this PR reorders a lot of instructions and CSRs