drm/i915/gt: Restrict gen7 w/a batch to Haswell

The residual w/a batch is causing system instablity on Ivybridge and
Baytrail under some workloads, so disable until resolved.

Closes: https://gitlab.freedesktop.org/drm/intel/issues/1405
Fixes: 47f8253d ("drm/i915/gen7: Clear all EU/L3 residual contexts")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Prathap Kumar Valsan <prathap.kumar.valsan@intel.com>
Cc: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200311103640.26572-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_ring_submission.c

@@ -2088,7 +2088,7 @@ int intel_ring_submission_setup(struct intel_engine_cs *engine)
 
 	GEM_BUG_ON(timeline->hwsp_ggtt != engine->status_page.vma);
 
-	if (IS_GEN(engine->i915, 7) && engine->class == RENDER_CLASS) {
+	if (IS_HASWELL(engine->i915) && engine->class == RENDER_CLASS) {
 		err = gen7_ctx_switch_bb_init(engine);
 		if (err)
 			goto err_ring_unpin;