[llvm] [RISCV] Rename rs1_wb to rd in some C instructions. NFC (PR #112269)

[Sam Elliott via llvm-commits]

https://github.com/lenary approved this pull request.

You likely missed C_SRLI64_HINT and C_SRAI64_HINT (noticed from the other PR), but overall this seems to be sensible

https://github.com/llvm/llvm-project/pull/112269