[llvm] [LoongArch] Allow delayed decision for ADD/SUB relocations (PR #72960)

[WÁNG Xuěruì via llvm-commits]

xen0n wrote:

We may want to implement proper `R_LARCH_{ADD,SUB}_ULEB128` support to fix the problem for good. [The RISCV implementation by MaskRay](https://github.com/llvm/llvm-project/pull/72610) is something we can build upon.

https://github.com/llvm/llvm-project/pull/72960