remove support for yuv 411
remove support for yuv 411

Previously we attempted to convert 411 input. Remove support
because malformed 411 input can cause the conversion to crash.

BUG=webm:1386

Change-Id: I3d41465a94867ee7f8eaa43fb76beb41f8fa644b

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