drm/i915: Fix sdvo connector get_hw_state function

The active output is only the currently selected one, which does not
imply that it's actually enabled. Since we don't use the sdvo encoder
side dpms support, we need to check whether the chip-side sdvo port is
enabled instead.

v2: Fix up Bugzilla links.

v3: Simplify logic a bit (Chris).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=60138
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=63031
Cc: Egbert Eich <eich@pdx.freedesktop.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Egbert Eich <eich@pdx.freedesktop.org> (v2)
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_sdvo.c

@@ -1231,8 +1231,12 @@ static bool intel_sdvo_connector_get_hw_state(struct intel_connector *connector)
 	struct intel_sdvo_connector *intel_sdvo_connector =
 		to_intel_sdvo_connector(&connector->base);
 	struct intel_sdvo *intel_sdvo = intel_attached_sdvo(&connector->base);
+	struct drm_i915_private *dev_priv = intel_sdvo->base.base.dev->dev_private;
 	u16 active_outputs;
 
+	if (!(I915_READ(intel_sdvo->sdvo_reg) & SDVO_ENABLE))
+		return false;
+
 	intel_sdvo_get_active_outputs(intel_sdvo, &active_outputs);
 
 	if (active_outputs & intel_sdvo_connector->output_flag)