Camera2: fix sawtooth in camera preview

Under certain combination of preview/screen resolution, sawtooth is
seen on preview image. In setTransformMatrix(),
scaledTextureWidth/Height is unnecessarily rounded to integers,
losing precision. Removing the rounding fixes the problem.

CRs-Fixed: 705322
Change-Id: Ia78b012cf530528b3677a8684279862a81b145ed