Function predequant_nvfp4_to_fp8 

pub fn predequant_nvfp4_to_fp8(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    b_packed: DevicePtr,
    b_scale: DevicePtr,
    scale2: f32,
    b_fp8: DevicePtr,
    n: u32,
    k: u32,
    stream: u64,
) -> Result<()>