[media] vivid: fix test pattern movement for V4L2_FIELD_ALTERNATE

The successive TOP/BOTTOM fields did not move as they should: only
every other field actually changed position.

The cause was that the tpg needs to know if it is dealing with a
FIELD_ALTERNATE case since that requires slightly different handling.

So tell the TPG whether or not the field setting is for the ALTERNATE
case or not.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
diff --git a/drivers/media/platform/vivid/vivid-vid-cap.c b/drivers/media/platform/vivid/vivid-vid-cap.c
index 49f79a0..d41ac44 100644
--- a/drivers/media/platform/vivid/vivid-vid-cap.c
+++ b/drivers/media/platform/vivid/vivid-vid-cap.c
@@ -733,7 +733,10 @@
 	if (tpg_g_planes(&dev->tpg) > 1)
 		tpg_s_bytesperline(&dev->tpg, 1, mp->plane_fmt[1].bytesperline);
 	dev->field_cap = mp->field;
-	tpg_s_field(&dev->tpg, dev->field_cap);
+	if (dev->field_cap == V4L2_FIELD_ALTERNATE)
+		tpg_s_field(&dev->tpg, V4L2_FIELD_TOP, true);
+	else
+		tpg_s_field(&dev->tpg, dev->field_cap, false);
 	tpg_s_crop_compose(&dev->tpg, &dev->crop_cap, &dev->compose_cap);
 	tpg_s_fourcc(&dev->tpg, dev->fmt_cap->fourcc);
 	if (vivid_is_sdtv_cap(dev))