riscv64: Add instruction helpers (#6099)

* riscv64: Add helpers for `add`

* riscv64: Add helpers for `sub`

* riscv64: Add helpers for `sll`

* riscv64: Add helpers for `srl`

* riscv64: Add helpers for `sra`

* riscv64: Add helpers for `or`

* riscv64: Add helpers for `and`

* riscv64: Add helpers for `xor`

* riscv64: Add helpers for `addi`

* riscv64: Add helpers for `slli`

* riscv64: Add helpers for `srli`

* riscv64: Add helpers for `srai`

* riscv64: Add helpers for `ori`

* riscv64: Add helpers for `xori`

* riscv64: Add helpers for `andi`

* riscv64: Add helpers for `not`

* riscv64: Add helpers for `sltiu`

* riscv64: Add helpers for `seqz`

* riscv64: Add helpers for `addw`

* riscv64: Add helpers for `subw`

* riscv64: Add helpers for `sllw`

* riscv64: Add helpers for `slliw`

* riscv64: Add helpers for `srlw`

* riscv64: Add helpers for `srliw`

* riscv64: Add helpers for `sraw`

* riscv64: Add helpers for `sraiw`

* riscv64: Add helpers for `sltu`

* riscv64: Add helpers for `mul`

* riscv64: Add helpers for `mulh`

* riscv64: Add helpers for `mulhu`

* riscv64: Add helpers for `div`

* riscv64: Add helpers for `divu`

* riscv64: Add helpers for `rem`

* riscv64: Add helpers for `remu`

* riscv64: Add helpers for `mulw`

* riscv64: Add helpers for `divw`

* riscv64: Add helpers for `divuw`

* riscv64: Add helpers for `remw`

* riscv64: Add helpers for `remuw`

* riscv64: Add helpers for `neg`

* riscv64: Add helpers for `addiw`

* riscv64: Add helpers for `sext.w`

* riscv64: Add helpers for `fadd`

* riscv64: Add helpers for `fsub`

* riscv64: Add helpers for `fmul`

* riscv64: Add helpers for `fdiv`

* riscv64: Add helpers for `fsqrt`

* riscv64: Add helpers for `fmadd`

* riscv64: Add helpers for `fsgnj`

* riscv64: Add helpers for `fsgnjn`

* riscv64: Add helpers for `fsgnjx`

* riscv64: Add helpers for `fcvtds`

* riscv64: Add helpers for `fcvtsd`

* riscv64: Add helpers for `adduw`

* riscv64: Add helpers for `zext.w`

* riscv64: Add helpers for `andn`

* riscv64: Add helpers for `orn`

* riscv64: Add helpers for `clz`

* riscv64: Add helpers for `clzw`

* riscv64: Add helpers for `ctz`

* riscv64: Add helpers for `ctzw`

* riscv64: Add helpers for `cpop`

* riscv64: Add helpers for `max`

* riscv64: Add helpers for `feq`

* riscv64: Add helpers for `flt`

* riscv64: Add helpers for `fle`

* riscv64: Add helpers for `fgt`

* riscv64: Add helpers for `fge`

* riscv64: Add helpers for `sext.b`

* riscv64: Add helpers for `sext.h`

* riscv64: Add helpers for `zext.h`

* riscv64: Add helpers for `rol`

* riscv64: Add helpers for `rolw`

* riscv64: Add helpers for `ror`

* riscv64: Add helpers for `rorw`

* riscv64: Add helpers for `rev8`

* riscv64: Add helpers for `brev8`

* riscv64: Add helpers for `bseti`

* riscv64: Add helpers for `pack`

* riscv64: Add helpers for `packw`

* riscv64: Add helpers for `slli.uw`

* riscv64: Add helpers for `fabs`

* riscv64: Add helpers for `fneg`

Author: afonso360