[llvm] [Memory] Call __clear_cache in InvalidateInstructionCache on LoongArch (PR #67285)

[WÁNG Xuěruì via llvm-commits]

https://github.com/xen0n commented:

IIRC, `__clear_cache` is DBAR, and I think we need not only DBAR but also IBAR?

https://github.com/llvm/llvm-project/pull/67285