[InstCombine] convert bitwise (in)equality checks to logical ops (PR32401)

As discussed in:
https://bugs.llvm.org/show_bug.cgi?id=32401

we have a backend transform to undo this:
https://reviews.llvm.org/rL299542

when it's likely that the xor version leads to better codegen, but we want 
this form in IR for better analysis and simplification potential.

llvm-svn: 308031