[clang] [llvm] [LoongArch] Adjust LA64 data layout by using n32:64 in layout string (PR #93814)

[via llvm-commits]

wangleiat wrote:

> @wangleiat What do you think?

I think this is a good start, and we should make i32 truly legal on LoongArch64, just like RISC-V.

https://github.com/llvm/llvm-project/pull/93814