drm/i915: Don't apply WaVSThreadDispatchOverride on HSW

drm/i915: Don't apply WaVSThreadDispatchOverride on HSW

BSpec states that the thread override values set by
gen7_setup_fixed_func_scheduler() are invalid for HSW. So let's not
muck around with them.

Since gen7_setup_fixed_func_scheduler() now has two totally independent
parts, one for IVB and one for HSW, move the HSW part directly into
haswell_init_clock_gating().

Note tht there's another workaround by the name of
WaHSWVSRefCountFullforceMissDisable which basically claims that later
steppings don't need the fix, but since WaVSRefCountFullforceMissDisable
is listed to be needed for all steppings play it safe and keep applying
the workaround.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>