Created by: baojun-nervana

The upgraded version is compatible with mkldnn v1.0. It uses NGRAPH_USE_LEGACY_MKLDNN to switch between v0.x and v1.x. It currently set to be TRUE to use v0.x. When MKLDNN is upgraded to v1.x, it need to set to FALSE. https://github.com/PaddlePaddle/Paddle/blob/6a28f7e7933d92cc19891ef9726896a94b05a1c4/cmake/external/ngraph.cmake#L79

CC. @grygielski @LeoZhao-Intel @mozga-intel