drm/radeon: fix cursor corruption on DCE6 and newer

commit e521a290 upstream.

Aruba and newer gpu does not need the avivo cursor work around,
quite the opposite this work around lead to corruption.

agd5f: check DCE6 rather than ARUBA since the issue is DCE
version specific rather than family specific.
Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/radeon/radeon_cursor.c

@@ -238,7 +238,8 @@ int radeon_crtc_cursor_move(struct drm_crtc *crtc,
 		y = 0;
 	}
 
-	if (ASIC_IS_AVIVO(rdev)) {
+	/* fixed on DCE6 and newer */
+	if (ASIC_IS_AVIVO(rdev) && !ASIC_IS_DCE6(rdev)) {
 		int i = 0;
 		struct drm_crtc *crtc_p;