drm/i915/dvo: implement get_hw_state

Similar to the sdvo code we poke the dvo encoder whether the output is
active. Safe that dvo encoders are not standardized, so this requires
a new callback into the dvo chip driver.

Hence implement that for all 6 dvo drivers.

v2: With the newly added ns2501 we now have 6 dvo drivers instead of
just 5 ...

Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/dvo.h b/drivers/gpu/drm/i915/dvo.h
index 0fa839e..74b5efc 100644
--- a/drivers/gpu/drm/i915/dvo.h
+++ b/drivers/gpu/drm/i915/dvo.h
@@ -114,6 +114,12 @@
 	 */
 	enum drm_connector_status (*detect)(struct intel_dvo_device *dvo);
 
+	/*
+	 * Probe the current hw status, returning true if the connected output
+	 * is active.
+	 */
+	bool (*get_hw_state)(struct intel_dvo_device *dev);
+
 	/**
 	 * Query the device for the modes it provides.
 	 *