[WebAssembly] Fix R_WASM_FUNCTION_OFFSET_I32 relocation warnings

We were incorrectly used the symbol table version of the function rather
than the object-local version when checking the existing relocation
value.

This was causing erroneous warnings for comat symbols defined in
multiple object.s

Fixes: https://bugs.llvm.org/show_bug.cgi?id=40503

Differential Revision: https://reviews.llvm.org/D60928

llvm-svn: 358871