Support ChainerX in MNIST data parallel example
Support ChainerX in MNIST data parallel example

wkentaro/chainer,pfnet/chainer,hvy/chainer,niboshi/chainer,niboshi/chainer,chainer/chainer,keisuke-umezawa/chainer,wkentaro/chainer,niboshi/chainer,wkentaro/chainer,wkentaro/chainer,hvy/chainer,hvy/chainer,okuta/chainer,okuta/chainer,chainer/chainer,chainer/chainer,chainer/chainer,keisuke-umezawa/chainer,okuta/chainer,hvy/chainer,okuta/chainer,keisuke-umezawa/chainer,niboshi/chainer,keisuke-umezawa/chainer