…ailure.

OnNthEltsVecArgument was introduced in llvm in 62fd4d18

Before introduction of full  opaque pointers support in situations when
the frontend uses opaque pointers, but the backend still uses typed the
information about original kernel arguments pointer element types was
lost by spirv-translator and i8* was used instead. This is critical for
byval arguments, so these types must be restored using information from
genx.convert intrinsics.