[llvm] [loongarch][DAG][FREEZE] Fix crash when FREEZE a half(f16) type on loongarch (PR #107791)

[via llvm-commits]

wangleiat wrote:

Thanks.
Perhaps we should override this interface.
```
bool softPromoteHalfType() const override { return true; }
```
We currently do not have any parameter passing specifications for f16 types，this may also cause the generated code to not meet expectations.

https://github.com/llvm/llvm-project/pull/107791