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

[Lu Weining via llvm-commits]

SixWeining wrote:

> > Partially fix the handling
> 
> Why is this fix partial? Can it be complete?
> 
> I agree that psABI documenting the recommended algorithm will be great.

The wording `Partially` means if those 4 instructions are not in the same 4K-page the algorithm is wrong. Of course, if the psABI documents the recommended algorithm, this would be a complete fix.

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