[X86] lowerV8I16GeneralSingleInputShuffle - for splat PSHUFW+PSHUFD patterns, widen the splats to encourage combines#129854

RKSimon merged 2 commits intollvm:mainllvm/llvm-project:mainfrom

RKSimon:x86-widen-vXi16-splat-maskRKSimon/llvm-project:x86-widen-vXi16-splat-maskCopy head branch name to clipboard