[WebAssembly] Add sign extend instructions from atomics proposal

Select them from ISD::SIGN_EXTEND_INREG

Differential Revision: https://reviews.llvm.org/D37603

remove spurious change

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@313101 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed