drm/i915: Store port enum in intel_encoder

Storing the port enum in intel_encoder makes it convenient to know the
port attached to an encoder. Moving the port information up from
intel_digital_port to intel_encoder avoids unecessary intel_digital_port
access and handles MST encoders cleanly without requiring conditional
checks for them (thanks danvet).

v2:
Renamed the port enum member from 'attached_port' to 'port' (danvet)
Fixed missing initialization of port in intel_sdvo.c (danvet)

v3:
Fixed missing initialization of port in intel_crt.c (Ville)

v4:
Storing port for DVO encoders too.

Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Lyude <cpaul@redhat.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1474334681-22690-3-git-send-email-dhinakaran.pandiyan@intel.com
diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
index c551024..a061b00 100644
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -2981,6 +2981,7 @@
 	/* encoder type will be decided later */
 	intel_encoder = &intel_sdvo->base;
 	intel_encoder->type = INTEL_OUTPUT_SDVO;
+	intel_encoder->port = port;
 	drm_encoder_init(dev, &intel_encoder->base, &intel_sdvo_enc_funcs, 0,
 			 "SDVO %c", port_name(port));