Convert to unsigned int before left shift
Convert to unsigned int before left shift

This is to fix overflow when 128 is left shifted by 24.

Change-Id: Ibb5f6813536d985afa003a9848c0c3dd358955a7

ShiftMediaProject/libvpx,GrokImageCompression/aom,Topopiccione/libvpx,mbebenita/aom,mwgoldsmith/libvpx,GrokImageCompression/aom,mwgoldsmith/libvpx,webmproject/libvpx,mbebenita/aom,ShiftMediaProject/libvpx,Topopiccione/libvpx,Topopiccione/libvpx,smarter/aom,webmproject/libvpx,smarter/aom,mwgoldsmith/vpx,mwgoldsmith/libvpx,mbebenita/aom,Topopiccione/libvpx,luctrudeau/aom,mbebenita/aom,luctrudeau/aom,mbebenita/aom,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,GrokImageCompression/aom,mbebenita/aom,webmproject/libvpx,GrokImageCompression/aom,webmproject/libvpx,GrokImageCompression/aom,mwgoldsmith/vpx,Topopiccione/libvpx,smarter/aom,mwgoldsmith/vpx,mbebenita/aom,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,Topopiccione/libvpx,smarter/aom,mbebenita/aom,mwgoldsmith/libvpx,smarter/aom,luctrudeau/aom,luctrudeau/aom,mwgoldsmith/vpx,webmproject/libvpx,luctrudeau/aom,mwgoldsmith/vpx,webmproject/libvpx,mbebenita/aom,ShiftMediaProject/libvpx,smarter/aom,mwgoldsmith/vpx,luctrudeau/aom,GrokImageCompression/aom