drm/i915: don't call modeset_init_hw in i915_reset

It seems to blow up my ilk in all kinds of strange ways. And now that
we're no longer resetting the entire modeset state, it shouldn't be
necessary any longer.

This essentially reverts

commit f817586c
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Tue Apr 10 15:50:11 2012 +0200

    drm/i915: re-init modeset hw state after gpu reset

safe for the introduction of modeset_init_hw, that one is nice to
prevent code duplication between driver load and resume.

v2: Add a comment to the code to warn future travellers of the dragon
dungeon ahead, suggested by Chris Wilson.
Acked-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -904,10 +904,13 @@ int i915_reset(struct drm_device *dev)
 		i915_gem_context_init(dev);
 		i915_gem_init_ppgtt(dev);
 
-		mutex_unlock(&dev->struct_mutex);
+		/*
+		 * It would make sense to re-init all the other hw state, at
+		 * least the rps/rc6/emon init done within modeset_init_hw. For
+		 * some unknown reason, this blows up my ilk, so don't.
+		 */
 
-		if (drm_core_check_feature(dev, DRIVER_MODESET))
-			intel_modeset_init_hw(dev);
+		mutex_unlock(&dev->struct_mutex);
 
 		drm_irq_uninstall(dev);
 		drm_irq_install(dev);