compositor-drm: Avoid leak during output configuration error path

Signed-off-by: Rob Bradford <rob@linux.intel.com>

src/compositor-drm.c

@@ -2407,6 +2407,7 @@ output_section_done(void *data)
 		free(output_name);
 		free(output_mode);
 		free(output_transform);
+		free(output);
 		output_name = NULL;
 		output_mode = NULL;
 		output_transform = NULL;