vp8 blend: resolve missing declarations
vp8 blend: resolve missing declarations

Remove unused functions.

BUG=webm:1584

Change-Id: If7a49e920e12f7fca0541190b87e6dae510df05c

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