Fix conditions when to use cuDNN implementation.
Fix conditions when to use cuDNN implementation.

cupy/cupy,keisuke-umezawa/chainer,kiyukuta/chainer,anaruse/chainer,keisuke-umezawa/chainer,ktnyt/chainer,jnishi/chainer,niboshi/chainer,ktnyt/chainer,aonotas/chainer,rezoo/chainer,cupy/cupy,wkentaro/chainer,hvy/chainer,ktnyt/chainer,hvy/chainer,wkentaro/chainer,keisuke-umezawa/chainer,delta2323/chainer,okuta/chainer,ysekky/chainer,cupy/cupy,cupy/cupy,ktnyt/chainer,tkerola/chainer,niboshi/chainer,pfnet/chainer,niboshi/chainer,jnishi/chainer,jnishi/chainer,wkentaro/chainer,chainer/chainer,kashif/chainer,chainer/chainer,chainer/chainer,niboshi/chainer,ronekko/chainer,okuta/chainer,chainer/chainer,keisuke-umezawa/chainer,jnishi/chainer,okuta/chainer,hvy/chainer,okuta/chainer,hvy/chainer,wkentaro/chainer