The values for the fourcc format were correct, but applied to the
wrong register. With this change, video is now barely working again with
tm6000.

While here, let's remove, for now, the memset. This way, people can
have some image when testing this device.

Yet to be fixed: parts of the image frame are missed. As we don't clean
the buffers anymore, this is "recovered" by repeating the values from a
previous frame. The quality is bad, since the image pixels will contain
data from some previous frames, generating weird delay artifacts.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>