[llvm] Minor optimizations to DW_OP_LLVM_extract_bits_* (PR #163812)

[Shubham Sandeep Rastogi via llvm-commits]

rastogishubham wrote:

@jryans I agree, this PR doesn't seem like it would fit with the expression optimizer. It is separate, and looks good to me to land

https://github.com/llvm/llvm-project/pull/163812