drm/i915: resume MST after reading back hw state

Otherwise the MST resume paths can hit DPMS paths
which hit state checker paths, which hit WARN_ON,
because the state checker is inconsistent with the
hw.

This fixes a bunch of WARN_ON's on resume after
undocking.
Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/i915_drv.c

@@ -706,11 +706,12 @@ static int i915_drm_resume(struct drm_device *dev)
 			dev_priv->display.hpd_irq_setup(dev);
 		spin_unlock_irq(&dev_priv->irq_lock);
 
-		intel_dp_mst_resume(dev);
 		drm_modeset_lock_all(dev);
 		intel_modeset_setup_hw_state(dev, true);
 		drm_modeset_unlock_all(dev);
 
+		intel_dp_mst_resume(dev);
+
 		/*
 		 * ... but also need to make sure that hotplug processing
 		 * doesn't cause havoc. Like in the driver load code we don't