drm/radeon: move bl encoder assignment into bl init

commit 4cee6a90 upstream.

So that the bl encoder will be null if the GPU does not
control the backlight.
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[ luis: backported to 3.16:
  - change radeon_link_encoder_connector() instead of
    radeon_encoder_add_backlight() ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/gpu/drm/radeon/atombios_encoders.c

@@ -236,6 +236,7 @@ void radeon_atom_backlight_init(struct radeon_encoder *radeon_encoder,
 	backlight_update_status(bd);
 
 	DRM_INFO("radeon atom DIG backlight initialized\n");
+	rdev->mode_info.bl_encoder = radeon_encoder;
 
 	return;
 

drivers/gpu/drm/radeon/radeon_encoders.c

@@ -179,7 +179,6 @@ radeon_link_encoder_connector(struct drm_device *dev)
 						radeon_atom_backlight_init(radeon_encoder, connector);
 					else
 						radeon_legacy_backlight_init(radeon_encoder, connector);
-					rdev->mode_info.bl_encoder = radeon_encoder;
 				}
 			}
 		}

drivers/gpu/drm/radeon/radeon_legacy_encoders.c

@@ -441,6 +441,7 @@ void radeon_legacy_backlight_init(struct radeon_encoder *radeon_encoder,
 	backlight_update_status(bd);
 
 	DRM_INFO("radeon legacy LVDS backlight initialized\n");
+	rdev->mode_info.bl_encoder = radeon_encoder;
 
 	return;