[WebAssembly] Fix broken assumption that all bitcasts are to functions types

Specifically, we can bitcast to void.

Fixes PR39591

Differential Revision: https://reviews.llvm.org/D54447

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@346778 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed