tiny_ssim: fix for odd image sizes.
tiny_ssim: fix for odd image sizes.

Change-Id: I7dd1e37c5de3efccc07fcdc877653d4873a88266

webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx