DRM/I915: Add enum hpd_pin to intel_encoder.

To clean up hotplug support we add a new enum to intel_encoder:
enum hpd_pin. It allows the encoder to request a hpd line but leave
the details which IRQ is responsible on which chipset generation
to i915_irq.c.
This way requesting hotplug support will become really simple on
the encoder/connector level.

Signed-off-by: Egbert Eich <eich@suse.de>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 2f2ec42..c7c5635 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -2821,18 +2821,22 @@
 	/* Set up the DDC bus. */
 	switch (port) {
 	case PORT_A:
+		intel_encoder->hpd_pin = HPD_PORT_A;
 		name = "DPDDC-A";
 		break;
 	case PORT_B:
 		dev_priv->hotplug_supported_mask |= PORTB_HOTPLUG_INT_STATUS;
+		intel_encoder->hpd_pin = HPD_PORT_B;
 		name = "DPDDC-B";
 		break;
 	case PORT_C:
 		dev_priv->hotplug_supported_mask |= PORTC_HOTPLUG_INT_STATUS;
+		intel_encoder->hpd_pin = HPD_PORT_C;
 		name = "DPDDC-C";
 		break;
 	case PORT_D:
 		dev_priv->hotplug_supported_mask |= PORTD_HOTPLUG_INT_STATUS;
+		intel_encoder->hpd_pin = HPD_PORT_D;
 		name = "DPDDC-D";
 		break;
 	default: