FADNet tensor size mismatched about openstereo

[ralph0813]

For ETH3D， you can use following transform setting:

    val:
      - type: StereoPad
        size: [ 512, 960 ]
      - type: GetValidDispa
        max_disp: 192
      - type: TransposeImage
      - type: ToTensor
      - type: NormalizeImage
        mean: [ 0.485, 0.456, 0.406 ]
        std: [ 0.229, 0.224, 0.225 ]

For most models, the input image size needs to be a multiple of 64 or 32. So generally speaking, using StereoPad and setting a reasonable size will do the trick.