[lld] [lld][LoongArch] Partially fix the handling of R_LARCH_PCALA64_* relocs (PR #73387)

[Rui Ueyama via llvm-commits]

rui314 wrote:

It looks like bfd and mold use essentially the same logic. If you believe their logic is correct, why don't you just copy that logic too? Doing that eliminates the need to check the code to see if the new code would produce the same output as the others for all possible inputs.

https://github.com/llvm/llvm-project/pull/73387