[Autoscheduler] Why no winograd for NCHW layout?

Hi @masahi I implemented it winograd for NCHW during ansor development too. But because we mainly optimize for NHWC layout(find it better on cpu and gpu), so we don’t enable it for NCHW when we upstream. This is the same reason as we mainly optimize NHWC layout on other hardwares (like mali / arm…), not only just winogrod.