drm/radeon/kms: fix legacy tv-out pal mode

fixes fdo bug 26915

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/radeon_legacy_tv.c b/drivers/gpu/drm/radeon/radeon_legacy_tv.c
index f2ed27c..0320403 100644
--- a/drivers/gpu/drm/radeon/radeon_legacy_tv.c
+++ b/drivers/gpu/drm/radeon/radeon_legacy_tv.c
@@ -642,8 +642,8 @@
 	}
 	flicker_removal = (tmp + 500) / 1000;
 
-	if (flicker_removal < 2)
-		flicker_removal = 2;
+	if (flicker_removal < 3)
+		flicker_removal = 3;
 	for (i = 0; i < ARRAY_SIZE(SLOPE_limit); ++i) {
 		if (flicker_removal == SLOPE_limit[i])
 			break;