drm/radeon/kms: only expose underscan on avivo chips

R4xx also uses the atom add connector function, but underscan is only
supported on avivo chips.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/radeon_encoders.c b/drivers/gpu/drm/radeon/radeon_encoders.c
index 4a4ff98..263c809 100644
--- a/drivers/gpu/drm/radeon/radeon_encoders.c
+++ b/drivers/gpu/drm/radeon/radeon_encoders.c
@@ -1708,7 +1708,8 @@
 		} else {
 			drm_encoder_init(dev, encoder, &radeon_atom_enc_funcs, DRM_MODE_ENCODER_TMDS);
 			radeon_encoder->enc_priv = radeon_atombios_set_dig_info(radeon_encoder);
-			radeon_encoder->underscan_type = UNDERSCAN_AUTO;
+			if (ASIC_IS_AVIVO(rdev))
+				radeon_encoder->underscan_type = UNDERSCAN_AUTO;
 		}
 		drm_encoder_helper_add(encoder, &radeon_atom_dig_helper_funcs);
 		break;
@@ -1738,7 +1739,8 @@
 		} else {
 			drm_encoder_init(dev, encoder, &radeon_atom_enc_funcs, DRM_MODE_ENCODER_TMDS);
 			radeon_encoder->enc_priv = radeon_atombios_set_dig_info(radeon_encoder);
-			radeon_encoder->underscan_type = UNDERSCAN_AUTO;
+			if (ASIC_IS_AVIVO(rdev))
+				radeon_encoder->underscan_type = UNDERSCAN_AUTO;
 		}
 		drm_encoder_helper_add(encoder, &radeon_atom_dig_helper_funcs);
 		break;