[GlobalISel][Legalizer] Fix legalization of llvm.smul.with.overflow

Previously the code for handling G_SMULO didn't properly check for the signed
multiply overflow, instead treating it the same as the unsigned G_UMULO.

Fixes PR35800.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321690 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed