Standard-to-LLVM conversion: check that operands have LLVM types

In Standard to LLVM dialect conversion, the binary op conversion pattern
implicitly assumed some operands were of LLVM IR dialect type. This is not
necessarily true, for example if the Ops that produce those operands did not
match the existing convresion patterns. Check if all operands are of LLVM IR
dialect type and if not, fail to patch the binary op pattern.

Closes tensorflow/mlir#168

PiperOrigin-RevId: 274063207