[lld] [llvm] [RISCV] Fix alignment when mixing rvc/norvc relax/norelax code (PR #150159)

[Kito Cheng via llvm-commits]

kito-cheng wrote:

Changes:
- Add `const` to `MCSection*` for the `RelaxEverSections` and `RVCEverSections`
- Fix and simplify condition in `RISCVAsmBackend::relaxAlign`.
- Drop lld tests.
- Adding MC tests


https://github.com/llvm/llvm-project/pull/150159