drm/i915: Enable hotplug interrupts after querying hw capabilities.

sdvo->hotplug_active is initialised during intel_sdvo_setup_outputs(),
and so we never enabled the hotplug interrupts on SDVO as we were
checking too early.

This regression has been introduced somewhere in the hpd rework for
the storm detection and handling starting with

commit 1d843f9de4
Author: Egbert Eich <eich@suse.de>
Date:   Mon Feb 25 12:06:49 2013 -0500

    DRM/I915: Add enum hpd_pin to intel_encoder.

and the follow-up patches to use the new encoder->hpd_pin variable for
the different irq setup functions.

The problem is that encoder->hpd_pin was set up _before_ the output
setup was done and so before we could assess the hotplug capabilities
of the outputs on an sdvo encoder.

Reported-by: Alex Fiestas <afiestas@kde.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=58405
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: Add regression note.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_sdvo.c

@@ -2790,14 +2790,6 @@ bool intel_sdvo_init(struct drm_device *dev, uint32_t sdvo_reg, bool is_sdvob)
 			SDVOB_HOTPLUG_INT_STATUS_I915 : SDVOC_HOTPLUG_INT_STATUS_I915;
 	}
 
-	/* Only enable the hotplug irq if we need it, to work around noisy
-	 * hotplug lines.
-	 */
-	if (intel_sdvo->hotplug_active) {
-		intel_encoder->hpd_pin =
-			intel_sdvo->is_sdvob ?  HPD_SDVO_B : HPD_SDVO_C;
-	}
-
 	intel_encoder->compute_config = intel_sdvo_compute_config;
 	intel_encoder->disable = intel_disable_sdvo;
 	intel_encoder->mode_set = intel_sdvo_mode_set;
@@ -2816,6 +2808,14 @@ bool intel_sdvo_init(struct drm_device *dev, uint32_t sdvo_reg, bool is_sdvob)
 		goto err_output;
 	}
 
+	/* Only enable the hotplug irq if we need it, to work around noisy
+	 * hotplug lines.
+	 */
+	if (intel_sdvo->hotplug_active) {
+		intel_encoder->hpd_pin =
+			intel_sdvo->is_sdvob ?  HPD_SDVO_B : HPD_SDVO_C;
+	}
+
 	/*
 	 * Cloning SDVO with anything is often impossible, since the SDVO
 	 * encoder can request a special input timing mode. And even if that's