[llvm] [DAG] getOperationAction - always return Custom action for target opcodes (PR #95401)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

I'm not sure I agree, always treating target opcodes as Custom makes more general sense to me. Tweaking combineFP_ROUND is just avoiding the problem surely?

https://github.com/llvm/llvm-project/pull/95401