[X86][SSE] Reduce instruction/register usages for v4i32 vector shifts (PR37441)

As suggested by Fabian on PR37441, use PSHUFLW to extend shift amount types for use with PSRAD/PSRLD to reduce register pressure.

Some of this ideally would be done by combineTargetShuffle but its tricky to do as most of the shuffles are sharing inputs.

Differential Revision: https://reviews.llvm.org/D46959

llvm-svn: 332524