drm/i915: BUG() on unexpected HDMI register

This should never happen, but the silent "return" makes me wonder
every time I try to debug InfoFrame bugs, so promote this to BUG() to
make sure people will complain if we ever break this.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_hdmi.c

@@ -377,6 +377,7 @@ static void g4x_set_infoframes(struct drm_encoder *encoder,
 		port = VIDEO_DIP_PORT_C;
 		break;
 	default:
+		BUG();
 		return;
 	}
 
@@ -435,6 +436,7 @@ static void ibx_set_infoframes(struct drm_encoder *encoder,
 		port = VIDEO_DIP_PORT_D;
 		break;
 	default:
+		BUG();
 		return;
 	}