[X86][SSE] Fix memory folding of (v)roundsd / (v)roundss

We only had partial memory folding support for the intrinsic definitions, and (as noted on PR27481) was causing FR32/FR64/VR128 mismatch errors with the machine verifier.

This patch adds missing memory folding support for both intrinsics and the ffloor/fnearbyint/fceil/frint/ftrunc patterns and in doing so fixes the failing machine verifier stack folding tests from PR27481.

Differential Revision: https://reviews.llvm.org/D23276

llvm-svn: 278106