Fix invalid OpIMul emitted for i1 multiplication (#3916)
OpIMul requires integer scalar/vector operands
OpTypeBool is not considered an integer type and causes spirv-val
failure
Inspired by https://github.com/llvm/llvm-project/pull/207388
Original commit:
https://github.com/KhronosGroup/SPIRV-LLVM-Translator/commit/3063fda0acb8f3c
