drm/i915: Change CHV WIZ hashing mode to 16x4

I ran a few tests with xonotic and synmark2 trying out the
different WIZ hashing modes on CHV. The results seem to match the
results I got with IVB/HSW when I did the similar tests on them
in the past. That is 16x4 is generally the fastest mode, 8x8 comes
next and finally 8x4. On CHV the difference between the modes is
at most ~1% in most tests. IIRC on IVB/HSW the difference was a little
bigger, but as there doesn't seem to be any real downside to 16x4
let's use it by default.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Arun Siluvery <arun.siluvery@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>