[llvm] [RISCV] Remove incomplete PRE_DEC/POST_DEC code for XTHeadMemIdx. (PR #76922)

[Wang Pengcheng via llvm-commits]

https://github.com/wangpc-pp commented:

I don't see any error and it seems that AArch64 is the same.
@zixuan-wu Please help double check this, thanks!

https://github.com/llvm/llvm-project/pull/76922