codecparsers: vc1: fix ttmbf when vstransform is not set

codecparsers: vc1: fix ttmbf when vstransform is not set

spec 8.3.6.2.1 Transform Type Selection
  If variable-sized transform coding is not enabled,
  then the 8x8 transform shall be used for all blocks.

I have to say the above spec isn't expressed clearly:
ttfrm is mentioned clearly, but not ttmbf.
anyway, since ttfrm is only specified when ttmbs is set,
we can deduce that ttmbf should set to 1.
it is also consistent with ffmpeg vc1 decoder and
hw behaviour (Intel GEN gfx)

https://bugzilla.gnome.org/show_bug.cgi?id=684341
https://bugs.tizen.org/jira/browse/TIVI-154