Update InitInput() in test/partial_idct_test.cc
Update InitInput() in test/partial_idct_test.cc

Make it work in high bit depth.

BUG=webm:1412

Change-Id: Ic5cfd410a69709f01e2924774356a108a349d273

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