drm/i915: transform INTEL_OUTPUT_* into an enum

Because I got annoyed that I had to document what values "int
ddi_personality" is supposed to hold.

A good side-effect of this change is that now the compilers can do
some additional checks on our code, which may prevent some bugs in the
future. A bad side-effect of this change is that now the compilers do
some additional checks on our code and complain when a switch
statement doesn't check for all possible values, so we need to add
"default" cases to all those switches. Hopefully, this may help
preventing confusions against DRM_MODE_CONNECTOR_* and
DRM_MODE_ENCODER_*.

I guess that just by looking at the patch, some people will think this
change is not worth its benefits. In this case, I don't really mind
dropping the patch.

Also, there's probably still a few more places where we can
s/int/enum intel_output_type/, but we can change that later, when we
spot the places.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
[danvet: Resolve conflict due to reordered patches.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index aeda09d..ee982f5 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6269,6 +6269,8 @@
 		case INTEL_OUTPUT_DSI:
 			is_dsi = true;
 			break;
+		default:
+			break;
 		}
 
 		num_connectors++;
@@ -6597,6 +6599,8 @@
 			if (enc_to_dig_port(&encoder->base)->port == PORT_A)
 				has_cpu_edp = true;
 			break;
+		default:
+			break;
 		}
 	}
 
@@ -6901,6 +6905,8 @@
 		case INTEL_OUTPUT_ANALOG:
 			has_vga = true;
 			break;
+		default:
+			break;
 		}
 	}
 
@@ -6934,6 +6940,8 @@
 		case INTEL_OUTPUT_LVDS:
 			is_lvds = true;
 			break;
+		default:
+			break;
 		}
 		num_connectors++;
 	}
@@ -7188,6 +7196,8 @@
 		case INTEL_OUTPUT_HDMI:
 			is_sdvo = true;
 			break;
+		default:
+			break;
 		}
 
 		num_connectors++;