anv: Disable the vertex cache when tessellating on SKL GT4

I have no idea if I'm correct about what's going wrong or if this is the
correct fix.  However, in my multiple weeks of banging my head on this
hang, a VUE reference counting bug seems to match all the symptoms and
it definitely fixes the hang.

Cc: mesa-stable@lists.freedesktop.org
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107280


Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
(cherry picked from commit b08b4b2b)