drm/i915: Give encoders useful names

Rather than let the core generate usless encoder names, let's pass in
something that actually identifies the piece of hardware we're dealing
with.

v2: Use 'DSI %c' instead of 'MIPI %c' for DSI encoders (Jani)
v3: Use port_name() in DSI code since we have it

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1464371966-15190-7-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index c454744..022b41d 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -2347,7 +2347,7 @@
 	encoder = &intel_encoder->base;
 
 	drm_encoder_init(dev, encoder, &intel_ddi_funcs,
-			 DRM_MODE_ENCODER_TMDS, NULL);
+			 DRM_MODE_ENCODER_TMDS, "DDI %c", port_name(port));
 
 	intel_encoder->compute_config = intel_ddi_compute_config;
 	intel_encoder->enable = intel_enable_ddi;