[WebAssembly] Fix uses of FrameIndex as store values

Previously the code assumed all uses of FI on loads and stores were as
addresses. This checks whether the use is the address or a value and
handles the latter case as it does for non-memory instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@259306 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed