i965: Disable 3DSTATE_WM_HZ_OP fields.

i965: Disable 3DSTATE_WM_HZ_OP fields.

Eric believes this to be wrong and unnecessary, as the command is
supposed to emit an implicit rectangle primitive.  However, empirically
the pixel pipeline is completely unreliable without it.  So for now, it
stays until someone comes up with a better solution.

We'll need to do better than this when we implement multisampling, HiZ,
or fast clears...but for now, this will do.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Acked-by: Eric Anholt <eric@anholt.net>