[llvm] [DAG][X86] Use pattern matching to simplify PSADBW+ADD combine (PR #147637)

[via llvm-commits]

woruyu wrote:

Hi @RKSimon , refactored the combine logic of `add(psadbw(X,0),psadbw(Y,0)) -> psadbw(add(X,Y),0)` using pattern matchers. Ready for review.

https://github.com/llvm/llvm-project/pull/147637